I was just thinking about these the other day. I used to use Polar Heart Rate monitor, but I find that works best if I'm walking, running, or other activity that's sustained. When I use it for a combo lifting/cardio, I get a bloated number.

I remember seeing on another Crossfit board (outside of MFP), that they aren't accurate for burning with CrossFit.

So, I am also interested in hearing about this.