A beeper for people who misplace their keys all the time.
One part of it is a small widget you put on your key ring. The other part is a remote you keep on the wall like a garage door opener, in a drawer, or whatever.
When you can't find your keys, you grab the remote, hit the button, and the widget on your key ring beeps so you can find it.
Later make adaptations for phone cases so you don't have to have friends call you to find your phone.
This shit's been invented