Exercise and reinforcing high rates of response?

How about getting one of those watches that is also a heart rate monitor? You get to set your hart rate range you want to be in. Then it beeps at you, and it shows you, if you fall outside of that range. And its individual, you can set your maximum rate, and then work out with 75% - 85% of your maximum heart rate. These monitors are used in spinning cles, and a decent one is under 50 bucks.