The Sound Activated keyfinder is The Clapper for your keys. Instead of charging through your house like a madman in the morning, a civilized clap (or conservative whistle) is all one needs to activate the keyfinder. Then, the alarm is activated and an LED light blinks with fervor to make sure you are not late to work...again.
For $11.60, the Sound Activated Keyfinder might be the cheapest unemployment insurance on the market. Then again, if you are the type who holds clapping parties or runs the neighborhood's summer whistle convention, you may have less trouble by just passing on this one.