We sort of had an argument about the use of these things on this site a year or so ago. As it turned out, some of the people saw a great usefulness for these devices while the rest wondered what possible use they could have.
I think that the people who thought that they were very useful were those people who had never used them before. As it turned out those who bought and used them for a while (from the looks of it only a couple of weeks) discovered to their dismay that they really didn't have a great usefulness and Craigslist is covered with them. I think that there are still people convince of their usefulness "IF ONLY THEY WERE MORE ACCURATE" and that they are selling the $500 models so they can afford a $1,200 model. But most of the people saw that the information imparted doesn't even add much to professional racers who actually do not need to have a device to inform them of their form when they can clearly feel in on a long climb.
While there are still those who might think it useful I would like to know why you think it would be useful and what sort of knowledge do you think that it would impart that you could not detect simply through your legs without the extra weight of $500 in your wallet?