For the English version, with only a small poweriser scene, try Change Happenz.
Galileo got a sports medicine specialist hopping too. The verdict: Powerisers require a good level of health--muscle power and aerobic fitness--to use for long. In particular, a constant rocking motion is necessary to maintain balance when standing in place, so there is no real "resting" phase without a lamp post or buddy to lean on. But the Doc compared the stress on the body to riding a bicycle, finding no reason for the average person to fear joint or muscle problems from using the Poweriser. Another bit of good news: unlike skateboards and inline skates, the Powerisers are easy to stop by slightly changing the center of balance, simply allowing the spring to absorb the forward momentum. One note of caution: Although videos on several of the internet sales sites for these gadgets show stunts on steps, the tech-check (and the inventors) do advise that stairs should be avoided by anyone adverse to extreme-sport risks.
A pair of adult Powerisers will set you back about US$500 (€399), cheaper for kids. Yeah, it's a lot, but look at it from the green side: if you make that kind of investment it is less likely that these will take the route to the landfill via a long pause in the back of the garage or the cellar. FYI, Powerskip seems to be a similar product if you are in the market, but about twice as pricy.