My old Polar HRM died and there is no way of replacing the battery in the strap so I am looking at replacement options. I was thinking about getting the Garmin Vivoactive HR and adding a chest strap and speed and cadence sensors.

Due to having to watch my kids during the week, I do a lot of trainer miles during the week and then during the weekend, I hit the longer rides. For a bike computer, I have a Cateye double wireless with cadence and I also turn strava on on my phone when I go out for rides but that doesn't work well on the trainer. It would be nice if this new device would track GPS data on longer rides like century rides and such without having to kill the phone battery and then be able to upload/synch with strava after the ride and still do a good job of tracking the trainer sessions indoors.

I like the idea of using a fitness watch for the cycling stuff too as I like the idea of 24hr HRM, sleep data, and steps tracking and stuff so that is why I am thinking about going this route.

So my question is to anyone who is using this fitness watch or similar ones, what little nuances did you run into that might not have been brought up in the typical product reviews you find on CNET and other youtube type reviews especially ones related to cycling?