HRM-which one do you recommend?

I am having trouble recording my calories burned; I add treadmill calories and Nike+ calories (I walk on a 10% incline) then divide and log as almost 2 hours of walking just to get to the correct number. Who knows! I was advised to get a HRM and looked around a bit on amazon but it's all foreign to me. Do they track accurately? And which do you recommend? Thanks!