As opposed to yet another piece of electronics so I'll stress convergence of the existing ones. GPS actually handles most everything now (route planning and navigation, location, direction, elevation, time, etc.) but "wearable" GPS watches are huge and have limited displays and battery life, while handhelds get in the way, especially for those of us using trekking poles. So I wear a watch, too.

Since I can't divine a purpose for Fitbit I can't extrapolate it to backpacking, which by default is done outside of cell range, rendering most smart phone-linked devices moot. (Or is that mute?)

There's satellite communications, such as provided by SPOT, InReach and sat phones. Provide that minus the pound or more of dedicated gear and we're onto something.

Someone might want a wrist camera, but not I. I suppose one could siamese a Fitbit and a GoPro into a convergence device, but again its appeal to backpacking might be limited. We lack the downhill thrills, except for falling. Worst YouTube video ever.