I've seen things like this online, but I haven't found any combination of the two so I decided to share my findings and product.
This is a Oscilloscope and a power supply that you can get to run out, as much as I could think of, any audio jack that has the software to back it up :)
Let me introduce to you my plans...
First you will need the following:
Headphone cable with mic
Alligator clip wires x2
100k ohm resistor
30k ohm resistor (or close to it)
10k ohm resistor
A little piece of awg ~24 wire
Step 1: Cutting Up Your Headphone Set W/ Mic
You'll need a headphone set with a mic, the mic is very important because that is where the oscilloscope signal is fed. Check the tip and make sure it has 4 separate pieces; a tip and 3 rings. The tip is Left speaker, the first ring after the tip is the right speaker, the next ring is the ground and finally the fourth ring is the mic in most modern cases. (Note: your mic and ground might be opposite) [I found the pin setup on google images]
Crack open the mic part to reveal the juicy innards. Then snip off the mic, switch and speakers. Of course you can save this mic and the button and your speakers for something else. Leave a bit of speaker headphone wire as it needs to be a little longer for this project. Finally burn off a bit of the insulation and clean it with Isopropyl Alcohol.
Step 2: Oscilloscope Schematic
This is the basic Schematic. I use 2 resistors that add up to about 30k to go into the mic, and 100k to separate the com from the oscilloscope and then a 10k resistor to protect my phone.
Step 3: Assemble Oscilloscope
Solder your resistors in series, then solder them to your mic and ground respectively. (I'm a big solder newbie, so your things may not look like the blobjobs I did) xP
Cut a red and back alligator clipped cable we'll use one half for the oscilloscope, save the other have for later.
Solder these in place and your oscilloscope is done! On to the power output.
Step 4: The Voltage Quadrupler
Start by twisting up your headphone wires; you do not need to keep them separate. Take another length of wire and tin it up then wire it directly to ground.
While using some method to pump out a steady 2khz signal at max volume the power output of the headphones is only .5 volts ac. I wanted to get that up a little and get it rectified so that it can be more useful. Now for this, I tested various methods, including all sorts of transformers (which didn't work for me). This may be the case because the mic might be draining some current through the 110k resistors from ground. If you like you could make a dedicated power supply without the oscilloscope part and it may work better. I ended up choosing a voltage quadrupler which is also a rectifier, which you can find the schematic for here: http://www.daenotes.com/electronics/devices-circui...
I urge you to prototype your circuit out first as I did above. I ended up with a whoppppinggg 2.2 vdc. Not much, but it's something none the less.
If you're happy with it, solder it up.
Step 5: (Optional) the Enclousure
I like corrugated cardboard since it's abundant for me and free. so if you'd like you can follow these simple steps to copy my box.
First off cut out a cardboard shape that will fold into a box. I made my box 1.5"x3"x1.5 so the piece is 5.9"x3" [PLEASE NOTE: The .9" is because you must make the top side a bit short so that the lip can fit in and it will close nicely] with 1.5" squared squares 1.5 inches above the bottom and a little lip on top to close it with.
Next you need to fold it up effectively, so I razor blade (careful with razorblades) up the folding parts of the box using a ruler that I don't care much about (cause you might slip and ruin the ruler). [note, you need to mark through the sides where to cut on one of the planes because there is no obvious place to razor blade at; 4th image above]
Next cut slits to fit the wires out that will also serve to hold the wires in place because of the properties of cardboard.
Tie a knot in the audio cable so it wont ever slip through and place your cables in place.
Next, label it.
Lastly, hot glue gun it together. I used a bit of tape on the corner I was working on and let the hot glue drip down the corner. (lots of hot glue). Repeat this on each of the four corners and some along the bottom seam. then put a little bit of glue along the lip to hold it closed. [NOTE: Do not hot glue the lip closed, the glue along the end of the lip is only to make it grippy so that you can open and close it without it slipping open]
Step 6: Finished
That's it. Now to use the oscilloscope you will need some kind of app on your desktop or smartphone. To use the Power source you will need some kind of app or media that produces some semi-high frequency signal (I use 2khz) at max volume.
WARNING: I am not an expert. Although I give you the following. I have done research and judging by the power rating of the smallest SMD resistors I could find (which is .05watts) I hereby give my work with the use of smartphone or other handheld devices a questionable maximum power rating of no more than .025watts, that is no more than 15 volts, and that might even be way too high! Perhaps though, theoretically, you could go as high as 120 volts with a laptop/desktop, that would be 1.44 watts, (with 3 watt resistors in your Oscillo-Power build), but be very careful and test with expendable equipment. High voltage can arc and completely ruin electronics! Repeat, I am not an expert. Be careful and cautious.
That being said, God bless you and continue to work for the good of others! :)
Step 7: Update: Testing
I've uploaded a pic of me testing the voltage limit of the Oscillo-Power. This is the device hooked up to my atx type power supply 12v 48amp rail, it seems to work fine. I was even taking the pic with the phone while it was hooked up to the rail. I tested the Mic input by rigging the old mic into the Oscillo-Power with cables and it worked ok, there was a little interference I think from the 100k separator resistor, but I don't have another mic to test it with so that's the best I had. I think it's working properly. Now I reconnected it and I'm posting this post with the phone (Note II) while having my Oscillo-Power hooked up to the 12v rail and I just checked with my multimeter to confirm that it was indeed outputting 12v and it is 12.45v. Just to show that I was cautious myself, I did hook it up to my junkier smartphone earlier for a prelim. That's a confirmed operation for use with smartphones at 12v mission control.