Agreed, or when you're travelling, your passport .. few things are as important as that when you travel. Was on a family holiday recently and only found out it had gone missing upon check-in for the return flight.
Already been done. You can get Estimote Stickies (http://estimote.com). I go their larger Beacons when the first came out to play with there SDK. Works very nice :)
There's a few products available like this already... http://www.hongkiat.com/blog/bluetooth-tracking-devices/