Rumor has it that the next Apple Watch will include a GPS chipset. Assumedly, this would allow apps like Map My Run, Strava and others to track walks, runs and bike rides without relying on the iPhone for location data. With Apple Watch 2, people could just go for a run and have complete stats about it afterwards, all with their iPhone safe and sound back home on the kitchen table.
I do a fair amount of bike riding, on and off of paved streets. I use my Apple Watch to keep tabs on things like speed or distance mid-ride without needing to dig my iPhone out of the back pocket of my jersey.