Inspired by my wife China Blue's biomimetic firefly 2.0 artbot, I designed this simple firefly bracelet. It fits anyone from a small child to a large adult depending on high high up on your arm you wear it. We were selling these at the Providence Maker Faire and will sell them again at the NY Maker Faire in September (along with the Firefly 2.0 robots and the kits).
It is made of 3 simple stl files, designed on Rhino3d (the cuff is heavily borrowed from the beehive bracelet here on thingiverse), the upright body, the wings, and the cuff. After cleaning off the rafts and getting rid of excess plastic in the slit at the rear where the battery slides in (I used either a dremel or a pair of small scissors - it is a snug but not precise fit), wings are glued onto the back with hot melt glue, the bracelet to the belly, and simply clip the leads of any 3V flashing LED to about 4 mm, press it over the +/- faces of a 2032 coin battery and insert it into the posterior abdomen and you are ready to wear.