The Wind Up Rechargeable Battery stores your kinetic energy for later use. Actually it’s perfect for those of us who can’t sit still. Just crank on this for a few minutes every now and then, and bingo, lots of spare power for the MP3 player or phone. OK, so 2 minutes cranking for 6 minutes talk-time is not stellar conversion rate, but it’s better than nothing. $39.99.
Fully-charged, it can provide 2-5 hours of power for MP3 players, 5 hours of talk time, or up to 2 days standby time for a cell phone. Unlike other rechargeable batteries on the market, a built-in voltage regulator provides a constant 5V output and protects your gadgets from power surges. Takes 8 hrs to fully charge 600 milliamp battery using AC adapter. Powers most digital music players including iPods, handheld games, cell phones, PDA’s and USB powered devices.