A Bluetooth tracker that lives on the temple of your glasses.
Glasses get lost far more often than keys, and they are the one thing you cannot look for without them. Existing trackers are too thick and too heavy to hang off an eyeglass frame.
A slim silicone sleeve that slides over the temple tip of any pair of glasses and hides a tiny tracker inside. A curved lithium cell and a Bluetooth board sit in a foam-isolated shell, with pogo-pin pads for charging. Three sleeve sizes cover most frames.
Antenna tuning inside the sleeve and a battery-life test on real frames.