I've lost my spare key and I know it's somewhere in the house (I think I hid it from my wife and can't remember where I hid it). Anyone have any ideas how to make a locator? Does the key send out regular RF pings, or does it just respond to regular pings from the car? It must be one or the other in order for walk-up door handles to work. If it's the former, I think it will be an easy project. The latter would be more difficult, but doable. If I could at least narrow it down within 30 feet or so, it would help a lot.