showed a comparison between the Mio and a chest-strap HRM, and they were pretty close to right on. Apparently the fit is very important for a wrist-worn model, and Mio seems to have that down pretty well. Mio is also waterproof, so it seems like it would work for your needs. I'll keep poking around, but it looks like the Mio is the best option for wrist-worn on the market. If I find anything negative I'll post it for you.