From the wish-I'd-thought-of-that department: the Flashbag. Designed by Dima Komissarov, it's a standard USB flash drive that has a tiny pump in it that inflates when you load it with data. So if your drive is full of stuff, it blows up like a balloon, but if it's empty it remains flat and rectangular. It'll stay inflated even when powered down, so you'll be able to estimate how many more MP3s you can leech from your friend's computer just by taking a gander. Unfortunately, the Flashbag is merely a concept design and there are no plans at this time for it to be manufactured or sold. We hope some brave company will decide to start making them soon, for if there's anything the world needs, it's more bizarre USB devices.