Wireless Trackballs

[Voltron87]

Two things:

I want a wireless trackball mouse. What is a good relatively inexpensive one, and a good nice one? I'll pay for a nice one but I'll probably get a cheap one to start to try out and have as a backup. This will all be USB, right?

And will using a trackball help or hurt my ergonomics? I don't have any problems but I play a lot and want to keep on the right side of things.