Any suggestions on what kind of HRM I should buy?

So, I've reached my 5 lb goal and my reward to myself is a heart rate monitor. I need to look into it because I don't know much about them. I was wondering if anyone had any suggestions on what a good brand or kind would be? I'm hoping not too expensive and convenient. Mostly I just want it to calculate calories accurately for me but it would also be nice to have a new exercise gadget:)