I think the popular concensus is that the wrist band HR monitors are not as accurate as "Polar" style monitors. The strap that fits around the chest actually picks up on the electrical activity of the heart, and in my own experience when using a treadmill with the built in HR monitor using the handles, I have found that the Polar monitor is more accurate than the treadmill. Hope this helps.
I think the popular concensus is that the wrist band HR monitors are not as accurate as "Polar" style monitors. The strap that fits around the chest actually picks up on the electrical activity of the heart, and in my own experience when using a treadmill with the built in HR monitor using the handles, I have found that the Polar monitor is more accurate than the treadmill. Hope this helps.