bKey doesn't have a cable, and clips onto your key ring, so it's a lot easier to remember than other mobile chargers. It's even shaped like a key, so will look right at home on your key ring.
Take the cover off each end, and you'll see a USB connection for charging the bKey, and either a microUSB or Lightning adapter on the other (depending on whether you go for the iOS or Android version). Plug the bKey into your device and it'll juice it up, with no wires, and no need to hunt for a wall socket.
Its rubberised case should withstand all the bumps and knocks that come with everyday use, and means it won't get scratched by your normal keys in your pocket. It comes in black or white.
So what's the downside? Unfortunately, it won't boost your handset back up to full charge. Because of its size, it only has a 230mAh battery, which should give you 30 extra minutes of talk, surf or text time. Which is handy when you're in a tight spot, but it won't keep your phone going for a whole weekend away.
Still, as a quick juice-me-up on the go it's hard to fault. It's already surpassed its funding target on Kickstarter, so if you want one, pledge $20CAD (£11), and you'll never be cut off during that essential call again.