Someone on instructables has posted DIY instructions on how to create a 'Breath Powered USB Charger'. It actually works on the movement of your chest when breathing, and not exhaled air.
Using some parts scavenged from an old CD-ROM drive, a simple electronic circuit, and a few rubber bands you will soon be huffing and puffing your way to fully-charged pseudo-useful electronic gadget nirvana.You strap this thing around your chest, and the system uses the slight chest expansion while breathing to get some gears turning, and eventually, a small charge generated. If you wear one to work tell people it's responsible for keeping a "very serious condition" from killing you. Then they'll bring you all sorts of "get well" cookies/flowers/balloons. You take these, discard the cards, and give them to your girlfriend back home. Tell her you love her (even if you don't), and hope for sex. Breath Powered USB Charger and Sex Generator.
Breath Powered USB Charger [instructables]