For the naysayers.........you can often get used meters on Ebay for like $250. Some folks blow that on some high end shorts and top.
I've got two used Stages meters. Never an issue in years. I spent under $200 on one and about $250 on the other one.
A meter......just count the KJ's as-is.
HR is wildly inaccurate for calorie count. HR responds slowly to peaks and valleys in your work. You could be slowly bringing the HR down a hill for a minute or two but doing ZERO work. But guess what, as your HR ramps down you still accumulate calories. A meter doesn't accumulate anything in that scenario.