Compass no, but I use the the heading in my "Distance To Start" to point in the direction you should go to get back to the start position.
And at least for the 920xt, the heading is pretty good... as long as you move. When you stand still, it is not so fantastic. I haven't heard anything from users of other devices, so I assume that the heading is just as good/bad for them :)
Without an electronic compass, GPS direction/heading can be unreliable when you're standing still. Your GPS position is constantly shifting around due to things that can affect GPS accuracy (view of the sky, signal errors, number of visible satellites, etc.). The GPS doesn't know when you're not moving, so those position errors can be interpreted as movement and cause the heading to jump around.
I imagine that our devices do some filtering at a lower level to help mitigate this effect, but I don't know any specifics. Off the top of my head, you could establish a filter of your own that would do something like prevent heading updates based on movement speed over a period of time. The only drawback is that there might be a few seconds lag between the start of movement and the first heading update, depending on how you decided to implement this. There may be other or better ways of dealing with this, too.
I've used it with my compass widget here. I've not tested on an physical vivoactive device, so I'm curious how well it works.
I did notice that when developing my app north appeared to be in alignment with what I expect, but now that I've updated to the 3.20 firmware on my 920xt and a few days have passed it appears to be indicate north is more north-east than I expect.
