My friends over at Gizoo have just started their own blog. One of their first posts is about the Xlider and these things look very cool (though maybe not as cool as the Scarpar). The Xlider is a combination of roller blading and boarding. You have two small boards (one per foot) and each board has 2 Rollerblade like wheels.
They are “supposedly” simple to learn and come with an optional training cable to prevent you legs going off in different directions. By the looks of the Xlider videos you propel yourself like Blading, but as your not attached to the Xlider boards this opens various additional tricks.