Depending on your budget, you might look into the Gowear fit. This is a consumer version of a technology (bodybugg) often used in research studies where data on participants' daily caloric expenditures are needed. It tracks calories burned throughout the day (you can also track food, I think) through body heat, not just heartrate. It's supposedly quite accurate compared to even more expensive clinical technology.
Note that in order to access the data the gowear collects, you have to buy a monthly subscription. The subscription is on the order of $7/month, and 3-6 months' subscription often gets thrown into package deals and sales. Many people use the gowear for 3-6 months and then resell it, because by that point they have a pretty good idea of how many calories they burn in a day through day-to-day activity, exercise, even sleep.
I don't have any insight on "regular" heart rate monitors, because it's been 15 years since I've used one. Back then, it was Polar or Polar. I assume the technology & the market has changed a wee bit since then.
//b. strong
Kim
PS. I'm not affiliated in any way with gowear or its manufacturer.