The Freestyle Dirtsurfer, a hyprid between a skateboard and a bike, appears to be a winning combo of the best of both worlds. It is more flexible than a bike and more powerful than a skateboard.
Supposedly these Dirtsurfers are much easier to ride than skateboards. Interestingly, the faster you go, the more stable they become, thanks to their larger wheels and 'patented' steering mechanism.
You control the speed via a 'simple lever-activated disk brake mounted on the rear wheel'. You can acheive powerful braking by leaning towards the rear.
I don't have much experience with skating or snow boarding, but I would sure like to try this one.
The Freestyle Dirtsurfer sells for $450.