I am really not into training. I also not imagined that I would care about the fitness applications at Pebble. The only thing I used to check on my present watch was the number of steps/day. Pebble presents everything in a such a nice way, that I can't resist to get involved.
In the latest update of Pebble OS (I have v3.13 and a Pebble Time Steel) a new tab for Health was installed in the mobile app. At the watch, you can access the data via the Time Line, i.e. when the watch has it's start screen activated (the watch screen) and you press the up and down buttons. Everything is automatically registered. I don't have to say: "I'm going to sleep!" but the it works as any other activity band.
Pebble may also sync with Google Fit, which can be set under Settings in Pebble Health.
with that said: Pebble is a really competent fitness watch. The upcoming Pebble Time 2 also has a heart rate monitor, for those of you who need that.