Remember back when everyone owned a pair of rollerblades? How about several decades before that, when kids still strapped roller skates onto their shoes? Well, the California-based Cardiff Skate Company has sort of combined the one device with the other, in the form of its appropriately-named Cardiff Skate.
Like the strap-on roller skates of days gone by, the Cardiff Skate attaches to the user's existing footwear. The idea is that people can use the skates to get to their destination, without having to pack along a separate pair of shoes to change into once they get there.
Instead of leather straps and metal buckles, however, the skates utilize a downhill-ski-like ratcheting binding system. Sizing is accomplished through a spring-mount system, in which the front part of the skate automatically slides back to meet the front of the user's shoe, as soon as they step down.
The skates roll on three rollerblade wheels, arranged in a delta formation – a fourth rear wheel serves only as the brake. According to the company, this configuration "gives the user unique maneuverability and excellent stabilization while both skating and braking."
The Cardiff Skate is available in two sizes, both of which are priced at US$160. It can be seen in action in the video below.
Source: Cardiff Skate Company
xc skeleton - powerslide 2013 -powerslide.com
Same theory w/ the shoes, but inline style