I designed this to fit most devices, regardless of what phone / case someone has. It has multiple phone and body mounting options for versatility, and this Instructable will cover those details, and how to get good video.

Supplies

3D Printer

(optional) Lanyard

(optional) Rubber band

(optional) Paracord or string

Step 1: Print the Part

It's public domain, available here:

https://www.prusaprinters.org/prints/32799-body-ca...

https://www.thingiverse.com/thing:4425722

PETG is preferred because it’s more forgiving of being bent out of shape, but I designed it to work with commonly available PLA.

Tested with PLA and PETG:

0.20mm layers
20% grid infill
no supports
brim build plate adhesion

Step 2: Attachment Methods

It was designed to clip to your shirt, but here's a rundown on other options I've tried.

Clipped to your shirt:

Pros:

1. Most stable video, on par with holding in your hand (up to a slow jog in my testing)

2. No extra parts

Cons:

1. Pulls the neck of your shirt down

2. Cumbersome to check your phone

Clipped to a lanyard:

Pros:

1. Easier to check your phone

2. 2nd most stable video, when using a shorter lanyard

Cons:

1. Hard to get a shorter lanyard on/off

2. Extra parts

Secured to a backpack or messenger bag strap:

Pros:

Most comfortable

Cons:

1. Least stable video

2. Extra parts and setup

3. Not recommended for narrow phones

Step 3: (option) Setup for Backpack or Messenger Bag Mount

Backpack:

Feed a piece of string or cord through the mount's center hole, then loop it through the backpack's hanging loop and tie a square knot. The paracord or string should be about 24" / 60cm long.

The pressure between the strap and your body holds the clip fairly well, but keep in mind that sliding the clip left will frame the video to the right, and sliding the clip right will frame the video to the left.

Messenger Bag:

Set the part so the shirt clip is on the bottom of the strap, and run a string or cord through the shirt clip to a buckle. The weight of the phone will pull the other side down, and level it.

Step 4: (optional) Add a Rubber Band

Feed the rubber band through the center hole, around one of the clips, and tie a lark's head. It will give options for holding the phone more securely, but make it harder to get it in/out.

Step 5: Attach Your Phone

It should slide into the holders, but it's one size fits most. If it jiggles in the slot, or if it crackles when pulling the arms apart, stop.

Clip is too tight:

Mostly a problem with phones wider than ~80mm/3.15” getting into a PLA print. Try inserting the phone from one slot to the opposite corner.

Clip is too loose:

Mostly a problem with older phones (they were smaller) without a case, but the printed part can also get bent too far and come apart. If it’s a small phone, wrap a rubber band around one or both slots a few times, in a figure-8 pattern. If an arm was bent too far, don't use it.

Step 6: Recomendations for Best Results

Shaking is the enemy. To get the best video:

Use the widest angle your phone supports.
If shirt or lanyard mounted, place the phone in the middle of your chest, over your sternum
If strap mounted / portrait orientation, place the phone low in the clip, and make sure the bottom of the phone touches your body. This makes a triangle to keep the phone / video more stable.