Hydrogen fuel cells have been helping astronauts for nearly half a century already, so it's about time they became small enough -- and cheap enough -- to be of use to everyone else. That's exactly what Intelligent Energy claims to have achieved with its the latest fuel cell system, called the "Upp." At 500 grams and with a retail price of $199, it's not meant to compete with regular lithium ion battery packs -- in fact, the Upp behaves very differently.

For a start, you don't need to charge it. You just slap on a hydrogen cartridge and it's ready instantaneously. One cartridge yields around five charges for a smartphone, with each charge taking no longer than a mains USB charger would. When you're running low, an accompanying app either triggers the delivery of a new cartridge (perhaps by courier, if you've signed up to that sort of service) or directs you to the nearest store so you can exchange it. Unlike some other personal fuel cells we've seen, the Upp is a finished product that is ready for sale: the version we tried is ruggedly built and designed to work in the high temperatures of sub-Saharan Africa, where it'll initially be sold by mobile operators to customers in areas with unreliable electricity infrastructure. Check out our hands-on video to see it in action.