I haven't been on a treadmill in years, I walk/run outdoors. But if I recall it right if you are on the treadmill you need to put your hands on the bar to get your heartrate.
That might be kind of inaccurate, and I found it hard to keep my hands on that bar while walking or running.
I now have a Polar F6 which I really love. I had one of those fancy schmanzy ones before that I just found too difficult to operate, I just want to get my heartrate and how many calories I burned, my pedometer tracks the distance.
I think it depends on what you feel comfortable with.