HRM Help

Ok, so I know a lot of people are biased to their own HRM. However, I need some good opinions on what I might be looking for.
I want a thin one....not bulky.....one that doesn't need the chest strap, just the band (like a watch).
I'd want it to read HR AND calories burned.....BUT I don't want to have to press my fingertips on it for several seconds for it to keep updating. I'd like it to do it without me having to stop my workout for it to read.
Any ideas?