Attach the Hone device on your keychain. (It only weighs half an ounce, so it’s not too bulky). Then if you lose your keys, use the Hone app to help track them down. Use the app to trigger the search. Essentially, the Hone device has uses Bluetooth to find your missing keys if they are within a 150 foot radius of you and your iPhone or iPad. The device will beep and light up once its detected.
The device takes CR2032, a standard watch battery, which lasts for about six months. The system costs $59.99.