Polar Heart Rate monitor recommendations

None of them measure calories burned, they all estimate that from heart rate (and, in the case of fitness trackers, possibly GPS coordinates, altitude, arm movements, and more). They'll be more accurate in their estimates for some activities vs. others, or for some people vs. others . . . close enough for most of us.

If you do exercise that involves lots of arm flexion, you'll probably want to continue to use a chest belt during exercise, even if you get a wrist-based device for all-day tracking. My Garmin Vivoactive 3 seems to give me reasonably reliable heart rate data (compared to older devices, doctors' office checks, etc.) most of the time from the wrist sensor, but will lose wrist contact during rowing (on water or machine) to a degree that's unhelpful.

Probably any of the well-respected mainstream brands will give you reasonable steps estimates, though you may want to think about your particular routine and how it may affect ones that function in various ways. For example, some use arm movement to estimate steps, so if lots of your steps involve pushing a cart or baby carriage (no arm swing), they may underestimate . . . and some people find that those that use arm movement think they're walking when they're actually doing something like playing a musical instrument. If much of your walking is outdoors, a GPS-based device could be helpful. Some devices can be worn clipped on your body/bra/shoe, if that's desirable for you. Etc.

For any device with user settings or self-tests, you'll get more accurate results if you set those carefully. (Some allow you to set step length, for example, but will guess from your height - maybe incorrectly? - if you don't set it. If you have a tested HRmax, some devices will let you set that, or have a builtin test of some sort that helps improve what they do in that area.

Think about whether you want a device that works without your phone nearby (and what its storage capacity is), whether you want to have it show you notifications when your phone is in range for texts/calls and such, stores/plays back music, need it to work when you're in the water, etc.

I know this may seem super complicated, but it's really not. If you make a list of the kinds of exercise you do, and read some online reviews and vendor information from Polar, Garmin, Fitbit, etc., you'll get a feel for what features are available, what the cost range for them is, and which might be worth it to you.

Best wishes!