Introduction: Pee to Check-In to Foursquare - Mark Your Territory

About: I want computers to be wilder. Running a Jungle makerspace in Panama.…
In case you are unfamiliar with the most amazing new way to physically "check in" to foursquare here is a video that will explain it all:

Mark Your Territory is a fully open-source system but because it interacts with the physical world as well as the digital one, some construction is necessary beyond just simply downloading the app to your phone.

The main project site is here:

This project uses the brand new Android ADK (Accessory Development Kit) platform for combining Arduino input with an Android device. Thus the included source code is good to experiment with and provides a basic starting point for anyone getting into

-Android programming
-Arduino programming
-Using Google's new Accessory Development Kit
-Basic Sensing
-Using the foursquare API
-Printing colored designs with a laser cutter

(though my code is pretty messy)
If you are interested in the code aspect of this project check out the step labeled "Hacking the Code"

*NOTE: Remember that Physical Check-ins may not be recognized by many establishments. If you want to claim an area, stake something in the ground, or pee on property you don't own, you are taking your own legal risks. I'm not responsible for any kind of mess you may get yourself into.

Step 1: Materials Needed

In order to fully use the system you will need the following items:

1) Android Phone
with the MYT app:

2) Arduino board supporting the ADK (Android Development Kit)
compatible boards listed here:
(I use this one )

3) Arduino firmware for moisture sensing
Available here:

4) building/electronic/art materials
Silicone (not entirely necessary)
Cornstarch (not entirely necessary)
absorbent sturdy paper
spraypaint + laser cutter (or your own method of screen printing and cutting)
Silver Goauche
9 volt
clothes pin
Person specific plant seeds
heat press (or a bunch of heavy flat things)

Step 2: Theory

While many may consider this project rather ridiculous, the project is based upon an underlying design theory of embedding physical/natural systems into digital works.

In this world there are organisms and areas. Over billions of years complex, powerful systems evolved which enable the organisms to stake a claim upon a physical area in many different ways. All of these varying methods featured specific affordances and constraints which lead to powerful proliferation of information through the totality of an environment. A dog urinating on a tree, for instance, leaves not only the information that a specific animal had been to a place, but also data concerning the creatures physiology, stature, frequency of visits, and mood.

As humans developed language, we began to leave this rich system designed by our animal brethren and our other senses dulled. With advances in intra-human communication such as printing or rapid electronic communication came further separation from the rest of the physical world.

One of the latest manifestations of this digitally mediated human solipsism is Foursquare. In Foursquare, similacra of real-world locations are digitally overlain in which humans can easily communicate to each other if they (supposedly) visisted a particular place, and which person (supposedly) holds domination over this place by visisting it the most frequently.

Mark Your Territory is a new system that lets individuals check-in to foursquare by physically urinating at the actual location.
MYT maintains the abilities of Foursquare while drawing humans back into the physical world. It is not a shunning of digital technology, but instead serves as a patch, tying together the tear between the worlds of the physical and (Humans-only) digital.

By imposiving several carefully crafted constrains upon one's digital check-in, the new physical-check-in is imbued with several features drawn from real-world marking. Such features include:

Check-In Gradient
-How "there" were you?

Unbiased Profiles
-A description of yourself that you cannot cheat

Cross-Species Communication
-Squirrels knows nothing of your Foursquare status but can tell where you peed

True Ephemera
-Maintenance of a physical reputation is demanding (and rewarding)

Indirect Environmental Restructuring
-Explicit marks fade, but one's impact on a physical environment is permanent.

NOTE: Some of my oppenents maydeclare this project as "sexist design" and that females can't/won't use this system. I think this proves otherwise.

Females can also use the device in a squatting manner, with the aid of a peripheral such as the go-girl (, or by studying the standing techniques discussed in "A Woman's Guide on How to Pee Standing Up" .

Step 3: Create the Markers (Printing/Cutting)

These markers do more than just get peed on; they feature carefully designed affordances for claiming territory in hybrid digital/physical spaces.

At their core, they can stick in the ground and illustrate text and QR codes. The needs to be only revealed if it gets peed on well enough though. Let's see how to make this.

First I tested out various methods of getting an image to show up when wet (crayola color changing markers, litmus paper printing, wax burn-off). You can see the excellent full brainstorm discussion at

Eventually i went with the spraypaint/laser cuttter/ soluble gouache method as it produced the results with highest contrast.

Get nice thick rigid (yet absorbent) paper. I used water color paper.

Give a thin, even dusting of spray paint on one side.
Load up your design in illustrator ( the stencils I used are available here: )

Now when you laser cut onto the spray painted paper, it will cut through the thin layer of paint on top and reveal an inverse image of high contrast (and nice physical texture).

Step 4: Create the Markers (Litmus Paper)

Turning regular paper into litmus paper is bizarrely easy.

1) boil a ton of shredded cabbage in Deionized water (Not sure if this actually did anything but I used filtered water instead)

2) strain its purple juice into a collection jar

3) Pitch the shredded cabbage (I ate mine by blending with mashed potatoes to make purpley mashe potatoes)

4) soak your markers in the cooled juice for about 10 minutes (get each side evenly and watch out for floaty bits of cabbage)

5) Put them on a rack to dry evenly

6) Test out their color changing abilities. In theory people with more vegetarian diets pee more basic (blue) and meat-eaters tend to make them turn red.

Step 5: Create the Markers (Secret Message)

We need to make sure that some effort is put into people's urination, and reward them by revealing a message or QR code.

Laser cut (or regular cut) yourself a paper stencil that fits over the area you want to obscure.

Dilute your silver gouache a little bit and cover the marker with the stencil. Paint over the area and put onto a rack to dry.

Test one out after it dries to see if it works!

Step 6: Create the Markers (Embed Seeds)

After the product fully decomposes, it re-structures the environment in an echo of your impact of checking-in. In the future, the seeds will be genetically engineered to include a genetic watermark containing your personal data, and when people have portable gene scanners this will function much like QR codes do today. eg. You are walking around a forest and scan a forest of oak trees and your phone tells you that Andy was here 50 years ago at the ruins of this McDonald's.

To get this functionality going, here is what you need to do:

1) Get two sides of a marker prepped with a little bit of dirt and a couple of seeds

2) Glue two nails together a fixed width apart

3) Lay the nail over the marker and add a little bit of wood glue around the edges and up the middle

4) Cover the marker with its backside

5) Sandwich the product between other disposable papers and load into the heat press at 200 for 1.5 minutes (or put heavy books onto them for a long time).

Keep the nails in with the thing while it is being pressed to keep the attachment holes for the probe.

Step 7: Create the Markers (Sticky Back)

In the case of urban environments, you may want to attach your marker to a wall.
To make an adhesive backing, i sprayed the back with spray adhesive, let dry for 5 minutes exposed to the air (still tacky), and then covered with a thin plastic slip.

When you peel off the plastic, the adhesive is still ready to go

This guy may have good suggestions:

Step 8: Create the Sensor Probe

Building a moisture sensing circuit is about as easy as it gets.

First take two long wires and solder them to two conductive leads (i used two small nails)
Next, make your own sugru (, and attach the nails together at the same width that your nails were when you created the markers.

Don't make your attachment bulb as large as mine (it's kinda heavy).

Fork the wire at the end of the other probe and solder on a 10k resistor.
Bundle the long loose wires in a way that is nice (electrical tape or heat shrink tubing).
Attach to the appropriate ports on your Arduino.

Step 9: Start Marking

Connect your phone to your Arduino, power it on, and it should launch the app automatically!

Go to the spot you want to mark, connect a marker, select the foursquare venue in the app, and "activate" the check-in.

Step 10: Hacking the Code

My source code basically consists of hacking together several different systems (Arduino, Android, Foursquare). You can access all of it here:

I got a lot of help from some really great examples (and got really thrown off by some bad ones). You can look through my code, or browse some of these great samples yourself:

Arduino ADK Firmware
This was incredibly helpful for getting started with the ADK, as the "official" example code only worked if you had a very specific setup on your board. This serves as a much better "Hello World" for working with the ADK.

ADK Android Example
This is the official example that Google released. You can hack it up and get it to do what you want!

Using Foursquare with Android
This guy is great and even answers your questions about his code!

GPS and Android
Nice simple way to access your GPS coordinates
Hack It! Challenge

Runner Up in the
Hack It! Challenge

Pocket-Sized Contest

First Prize in the
Pocket-Sized Contest

4th Epilog Challenge

Second Prize in the
4th Epilog Challenge