I think you should get one and then hit the BMX track with it and let us know how well it goes. The guy riding the bike was on a beach without even as much as a hill insight and the people walking down the snow hill seemed to be moving faster then the snowboarder and sledders both.
Again, neat device I guess but not one I personally see very practical. $350 for a tethered selfie stick (camera NOT included), or about half the price as a blade 350 with a HD camera and not limited by the length of your string. To each their own though.
Really by the time you add the price of a Go-Pro you're going to be darn near at the price of a QX350 or over depending on which Go-Pro you get.