Auto-Pause when Smartwatch out of range?

[acaurora]

I just noticed this happening reently - at work I have Spotify on my phone playing to a bluetooth speaker. When I walk away (to go to the bathroom about 50 meters away, or to a meeting) and leave my phone on my desk, I return to find that Spotify has paused playback. 

I have noticed the only way how it can "tell" that I"m not there is because I wear a FitBit. Is this a hidden or new feature, or am I just crazy? o_O I mean, that's pretty cool, but it would be neat if it resumed playback once it reconnected to my phone...