The "Ski Mojo" is a wearable shock absorber that cradles the upper thigh, alleviating some of the stress the comes from skiing. MedGadget has a snotty quote from a "wintersports editor" at The Times of London about how these sorts of things are "in the same category as heated chairlift seats" which I think pretty much sums up my opinion on them: they sound great.
The Ski Mojo clips run around $600 a pair. Too bad they aren't less expensive. I'm sure they'd be most useful to those just learning to ski who haven't yet built up their stamina.