Cardiocoach.com...

I like them a lot. Bear in mind that I'm not quite the die-hard exerciser that some people here are. I find them motivating and easy to use and they make me work harder than I might otherwise. My instinct is that the first one might be too easy for you. I'd lean more towards the second or third one -whichever one is more geared toward intervals. Of course, since they're meant for use on indoor exercise equipment (that's not required, but it's how they're designed) you could just pop up the "level" higher than I do.

I have a few of these (1 and 2, perhaps.... I forget the numbers). if you want to borrow them, that would be fine. It might help you decide if you'd like to buy them. No pressure, but it's an offer.

Andrea