I purchased up3 a few weeks ago and could not be happier! Worked right out of the box; synced immediately with my phone. up3 was easy to set up and gives accurate hear rates ( I’ve checked and confirmed) ; bought primarily for Sleep monitoring and it did a great job and is better ( and probably safer) than having a iPhone next to my head all night using an App.
The software in the App is intuitive and quickly understood. Only downside would be the strap as does not seem that strong to be durable for a long time. All-in-all a great product for what I needed.