Heart Rate Monitors?

Options
I am pretty clueless about these but really want to be able to log my actual calories burned throughout the whole day, so that I can make sure I always end up with a calorie deficit. As a Phd student my daily routine can vary massively from sitting at a desk all day, to spending most of the day on my feet demonstrating or working in the lab (which for me involves lots of going up and down stairs!). So the calorie goal set by MFP should probably alter on a daily basis.

I also want to start a resistance training regime and am interested to see how many calories is actually burned during that.

Can you wear a HRM for the whole day and get the total calories burned at the end of it? I don't have much money - can anyone recommend any reasonably priced ones?

And advice would be much appreciated! I would love to plot actual calories burned with calories consumed and a daily weigh-in so that I can gauge the natural fluctuation of my weight and perhaps spot any patterns which might help further weight loss!