> If - at some point far, far in the future - cabs become obsolete, how will you get a ride when either your phone is dead far in the future, phones won't ever

> If - at some point far, far in the future - cabs become obsolete, how will you get a ride when either your phone is dead far in the future, phones won't ever be dead, unless you are dead. They'll be tiny, and powered by bodyheat or ambient heat or ambient radio waves or something. So this isn't a concern.