Heart rate monitor for tracking calories?

Hey all,

I am looking into purchasing a heart rate monitor to use in determining how many calories I am burning during workouts. I currently use a BodyMedia Fit armband (similar to a bodybugg) which is extremely accurate at many activities but not spinning! Sooooo, I have found a new love for spin but my device doesn't measure properly even after trying things suggested by the company.
I bought a heart rate monitor and lost my receipt and then realized it only uses steps taken to determine caloric burn despite also being a heart rate monitor???? ugh!
So, i am looking for something easy to use and obviously as accurate as possible.