Just like the iPhone 3G S, it shoots video and is voice-controlled. When you're dangling over a crevasse, you're fairly likely to need both hands -- one to hold on, and one to put a neat crease in your slacks -- so, if you spot a penguin tripping up another penguin, you simply shout 'action!' and the hilarity is captured for posterity.
The muvi shoots 640x480-pixel video in AVI format. It also takes 2-megapixel stills, and will work as a webcam. Everything is stored on a microSD card. You get a 2GB card in the box.
When you're done extreme horse jumping off cliffs and you've returned home for a well-deserved shower and a mug of Horlicks -- extreme Horlicks, naturally -- you simply plug the muvi in to your computer via USB, and it charges while you rub Vaseline on your saddle-chafed loins.
For an extra £20, you can also get an Extreme Sports Pack, including a weatherproof skin and assorted straps and clips, for mounting the muvi on handlebars, arms, walls and even your head.