If keeping your smartphones, tablets, and other gear running all day long is more important to you than keeping your backpack lightweight, the latest addition to Limeade's line-up of backup batteries—this 24,000mAh monstrosity should be part of your daily kit.
Surprisingly though, it doesn't take up much space. It will certainly be heavier than those tiny batteries designed to give your phone enough life to place a call or two, but the Limeade's added girth means it packs enough juice to full recharge an iPad twice over. That could keep you running for weeks.
It also has a pair of 2.4A USB ports so multiple devices can share in the extra power at the same time. While not specified, this backup battery will take a long time to fully charge—definitely an overnight affair—but that's well worth the trouble for an emergency backup that just won't quit. [Limefuel]
Updated: The Limeade doesn't appear to be available here in the UK yet (after the Kickstarter campaign ended in May 2013), but here's hoping that's changed soon. As ever, there are many ways you can circumnavigate US-only availability.