Princeton has addressed the need of longer battery lifetime with a portable battery pack that can recharge any portable USB device, including iPods.
The PMB-BP18 is a lightweight handheld device that allows you to plop that mobile phone or MP3 player down on the stand and juice it up. A green LED tracks the recharging process.
It can recharge two devices fully before it needs a plug-in, and its battery can perform 500 recharges before it needs replacing.
Look for it soon, for US$44.