Add heart rate to Fish game

[twait]

A heart rate display would be a great addition to the fish game.

I've added the game to my warm-up routine. However, it's easy for me to push too hard and get my heart rate into the 150's and 160's (which is a bit high if you're 58 and "average" athletically).

Having a heart rate display in the game would allow rowers to monitor their heart rate in that activity like they can in other rowing routines.