I'm curious about getting a trainer (is that what they are called?), but I honestly don't quite know exactly what they are. Yes I know, google it. And I will, but I'd rather ask another human being since I'll get some real opinions this way. I'm guessing they're a contraption to mount your bike on instead of buying an exercise bike. Will they work for virtually any bike (I have a Giant Boulder and my wife will probably have a cruiser/comfort bike this year)? How does it work? What are some good brands and general prices? Keep in mind that I don't drive a Cadillac nor do I have the money for Cadillac pricing, if you get my drift. thanx