Very lightweight. When used on your upper arm you will forget its there. No problems with bluetooth linking with an Android phone with the Polar app. Always connects fine, no drops. Storage (download) function also works great for using it without a phone. It will sync later when connected and upload that session to the cloud. The PC app also works well; all the cloud data appears there too. Only one minor issue is rapid phone battery drain while on. I forgot and left mine on for 5 hours and drained it to 36%. Had a Polar chest strap before and this works with way less hassle. Not going back.

Way back in the day I had a Polar chest strap. It was uncomfortable, got soaked with sweat every time I worked out, and was generally a pain in the bottom I put up with because It read my heart rate perfectly every single time.
Enter the new age of cool stuff; I got a wrist watch thingy to monitor my heart rate. Very convenient, measures heart rate 24/7, just stays on your wrist (athough you can't shower with it?) But wait: Every 3rd workout it dozes off and forgets to follow my heartrate, so when I should be doing the big push, instead I'm yelling at my wrist thingy. Then it quit, and you guessed it; right at the crux of my workout.
Enough! Unwilling to go on like this, I go on Amazon to see what else is available. I'm thinking I'll just bite the bullet and get a chest strap, but what's this? An armband HR monitor by POLAR? With great reviews? Oh, yea, I'm all in.
The software was a bit fidgety to set up, but now I know the drill for my devices and software; and every workout is the same. A glance at my heartrate verifies I'm on path, and afterwards I have graphic and digital records I can browse through to plot out recovery time and effort. This makes me very happy!
I wear mine on my left forearm and have never had to mess with the sensor to get a reading. It integrates with my Echelon bicycle running qdomyos-zwift and links with Stava.
Twelve stars!

I wanted this product for three reasons. In descending order of importance:
1) To connect to my Concept2 rowing machine and their Ergdata app so I could do heart rate zone training.
2) To wear when I was lifting or walking my dogs to monitor how many calories I burned.
3) To wear around all day and see how my heart rate fluctuated/how many calories I burned/steps I took.
I remembered the chest straps being somewhat cumbersome from when I worked at a gym like 20 years ago. And I'd read that the wrist monitors/smartwatches didn't work well for rowing. So I went with the Verity Sense.
While it was comfortable and did fulfill function #1 well, connecting easily with the rowing machine and the app and giving what seemed to be accurate readings, it was an utter failure otherwise.
A) Polar has two Android apps, Polar Beat and Polar Flow. There's no indication of which one to choose – one was made later, while the other was updated more recently. Only through a response to a negative review on the app store did a developer say that all effort is being put into Polar Flow.
B) Either way, neither app works. They constantly disconnect at random times, then tell you that some other app is using the monitor, even if you have no other apps open (and yes the rowing machine is off/in a different room). If you turn the device on and off, and close and reopen the app you may get a connection after 5-10 minutes.
C) Worse, there's no notification of this disconnection, so enjoy having only half of a workout tracked, or not tracking your daily activity for 8 hours.
D) The apps lacks any feature for daily tracking, instead you have to choose an activity from a list of ~600. Also there's no way to quickly peruse calories per day. (The log feature only shows max HR and time.)
Overall, the terrible functionality of their software caused me to put in a return for this product and steer clear of Polar in the future. I would urge them to hire more competent developers. Having apps that don't work renders the device unusable and not worth the high price.

This extremely lightweight heat rate monitor seems to work well. I use it for my running, and while I'm not sure it's quite as accurate as my old chest strap monitor, it does help guide me when it comes to exertion.
Phone connectivity was easy enough with the free Polar Flow app, though I'm not the biggest fan of the actual app. Fortunately, the monitor easily connects to a LOT of fitness apps. I use mine with Strava and Wahoo with no trouble.
The included arm strap is highly adjustable, so getting a good fit is easy. Charging it is a snap, too, with the included charging device, though I do think that the charger would be pretty easy to lose. Overall, though, I think it's fine.
I'm happy with this purchase and use mine daily. It's definitely worth looking into if you're in the market for a great rate monitor.