Heart rate monitoring watches

I've got a Fitbit Charge HR and love it. like Mrs Lannister i haven't done any comparison testing but i reckon it's fairly accurate with my heart rate.

Remember that HRMs are heartbeat counters and not calorie counters!

Polar FT7, nice watch, poor reliability, low level of functionality, short lifespan to sudden death!
Calorie counts probably overestimated by 10 - 20%, worst over-estimating when starting out not particularly fit.

Polar FT60, OK watch, good reliability, nice functionality, ability to customise/personalise settings. VO2 max estimator is a nice feature.
Appears very accurate for calorie estimates (*) once properly calibrated for my particular heartbeat range and VO2 max when used for an appropriate exercise under suitable conditions (only!). I had my true max HR and VO2 max tested in a sports science lab by the way.
(* = when compared against power meter equipped trainers.)

Garmin Edge cycle computer and HRM - reliable as a HRM. Calorie estimates generally on the low side varying to very low estimates for lower intensity long duration rides.

Forget tracking calories as "accurate" and aim for "reasonable" when used with a bit of common sense. All of the above gave usable calorie estimates in that there was enough consistency and proportionate to my effort if not accurate.

I have a Polar FT4 and as of last 15 days a Fitbit Surge. I am very happy with both of them, I wear my Fitbit everyday all day long to track my total expenditure of the day plus my workouts and I now have kept the Polar FT4 for only these days when I decide to hit the swimming pool (fitbit cannot be worn during swimming).

Honestly, heart rate monitors are the best fitness / exercise accessory I need! It really motivates me to do more and I have learned to train in different zones (aerobic, anaerobic).

Please take into consideration that no HR watch is 100% accurate but they're definitely more accurate from the generic MFP exercise entries and they are a great tool if you want to train indifferent heart rate zones.

I use the Garmin Forerunner 110. Yep, it's old, with a heart rate chest strap. I only use it during my runs. My heart rate really doesn't change that much during the day.

During my runs, I use heart rate to keep my pace at the desired speed for the work out performed. During the day, my I-Phone keeps track of my steps and I log other exercise in as it occurs. I also just log my runs as steps perhaps keeping the total depressed but it works for me.

I have a Garmin VivoActive HR, just upgraded from the VivoSmart HR, and I really like the unit. It's basically the Fenix 3 HR Jr.

The biggest thing to remember when you're using a GPS watch with a HRM.
1) The Optic HRM will be slower and more choppy than a Chest Best HRM for longer endurance activities.
2) The Optic HRM will be pretty much useless during strength training exercise due to the muscle flex.
3) All Caloric Burn is guesstimates anyway. Nothing is gospel truth when it comes to eating and burning calories.

I have the Garmin Vivosmart HR, and while it's fairly accurate, I find the more active I am, the less accurate it is (maybe because of position/movement/sweat?). I compare it to my HR strap, and there is often a difference.

That being said, I still like it and keep using it because it's more convenient and comfortable than a strap, and it tracks all day (HR while sleeping/resting HR is an important number).