I'm a big fan of Polar units but I don't recommend the CS200. It has (or maybe had) a flaky reputation for reliability.
You don't need a HRM to get motivated. Your rate of breathing is more than sufficient for determing how hard your working. A simple wired computer, with cadence, should be fine. But if you really want a nice HRM, look at the Suunto T3, which an be used for running, biking, etc., including wireless hookup to speed.The T2 isn't bad either.