Advanced RF MEMS. Wozniak was working on this a few years back. The latest "real worls" application is the tracking of "ZomBEES"

RF id tages small enough and cheap enough to place on bees to follow its travels.

Zombees reference:

http://www.treehugger.com/natural-sciences/parasite-found-be-turning-bees-suicidal-zombies.html

Imagine buying a baggie full of these tiny tags, placing them on things you miss place or that temporarily disappear such as car keys, wallet, your cheating wife, your philandering husband, grandma and grandpa, YOUR BEER and programming them into your phones GPS.