This is a small (tiny!) clip that slides around the cable on a pair of headphones, then slides over the front placket of a shirt (the part where buttons go).
This holds the headphones in-place between this clip and the wearer's ears, allowing freedom of movement without constantly pulling on the headphones.
I designed this as a test to see if something this small and detailed could be printed with any degree of success. In addition, it is a cool thing to make and use with all those white earbuds out there.
More back-story and details here: http://wp.me/p2hTaI-P
With the original attempt here: http://wp.me/p2hTaI-U
Print with desired settings (the object rotated to print without a raft or support. I printed at 100% infill with no extra shells.)
Slide headphone cable into either of the gap areas (thinner cables in the lower one).
Slide the two "arms" over a shirt placket.
Walk, jog, dance, whatever, without the earbuds coming out. Hopefully.