This is probably the most useful invention the Western world has seen since sliced bread or radar or et. al. As everyone knows, you're most likely to lose your keys when in a rush, at which point you're forced to decide between risking an unlocked front door all day or being late. No more. Rejoin, friends. Deliverance is here.
Meet the StickNFind, a quarter-sized sticker equipped with low-energy Bluetooth technology. You just put the sticker on your keys or your cat or whatever, then fire up the old smartphone (currently iPhones, iPads and Androids). Blam-o! You'll be presented with a radar-esque display showing where your items are in relation to you/one another.
Then just play the old game of "hot" or "cold," and make it to your meeting on time without leaving the front door open.
The stickers come with replaceable batteries that have a year's life estimate (with 30 minutes of daily average usage).