I bought this watch in April and I want to love it. The problem is that it has some problems. I live with those problems, but you may not want to. Here is my list of pros and cons:

Pros
More functions than any other smart watch I've seen. Including BP, O2 and Sleep monitoring
From what I've seen, the functions are fairly accurate
The Android app is very good and provides lots of options that include viewing all of your stats, battery life, finding the band (if it's connected), intelligent reminders and much more.
It's best value in a smart watch given it's features and low price

Cons
It requires GPS to link it to my phone (only a minor irritant)
The band connects to your wrist with a metal button that pops through one of the holes. The problem with that is the slightest pull on the end of the band will cause it to disconnect.and drop off your wrist. This has happened too many times for me to count.
The watch went stupid on me and stopped measuring sleep and steps. I had to factory reset the watch twice to get it to work again.
Now it vibrates on my wrist multiple times a day and when I look at it I see it cycling through all the functions. Time for another reset?
Even though the app has an option for firmware updates, I've yet to actually see one available.
The USB charging cable is not long enough and isn't a standard micro USB connector. Lose the cable and you're screwed.

In spite of the fairly significant faults, I put up with them continue to use it because I like it and it helps me monitor my BP throughout the day.
If I had it to do over, I'd still buy the watch, but I would really like to see a firmware update that fixes some of the problems. If that ever happens, I'll update my review.

Steve

It seems to work ok. The step counter isn't always accurate, or at least doesn't match up with the google fit app. And if the battery drops below 40% it sometimes stops recording data for sleep and steps. But the blood pressure, O2 and heart rate all match up with the numbers at the doctors office. It's hard to put on by myself and the band wears out quickly. Over all it was worth what I paid for it.
update 8/6/2017. The charger broke and I haven't been able to fix it. And the hole in the band that fit me has also worn out and the next one is too big for me. I still think it was worth what I paid for it, but I replaced it with another brand, one with an easier to find replacement charger and a replaceable band.

I have purchased this Heart Rate Fitness Tracker from GTSTAR to use.. It came with the watch and its charger.. For one good reason it was a good purchase was because of all the different functions that this one product can do.. It can does things like monitor all what you need to know to keep you healthy like your heart rate, pedo meter, blood pressure to name a few.. But to me this will really benefit people who is active and or sick so that they will have aome kind of help for the readings that tgis product offers.. All in all this is an awesome product to invest in..

I was dubious, but it absolutely works. I'm not sure how, but it does.

My BP was in range with typical Dr. office readings. I thought it might just be faking a reading so I tested BP on my wife. She is typically 20 points lower than mine. She tested 110/70, or about 23 points lower than mine!

I don't understand how it works, but this will pay for itself many times over vs just a HR, BP, or O2 devices.

Really impressed, especially for the cost.

Amazing wrist heart rate, very easy to hook up and work ! Fits on wrist very well and comfortable . Couldn't be any happier with this pick. This item is made very well and dirt proof, wear it everyday all day and seems to still stay clean and work very well. Long last life battery. Easy purchase and very fast shipment