No Uber - sorry - but if you stick the fona cab app on your phone (iOS also available) it will do the exact same job, except you'll need to pay cash.
What do you want from the city? Good food? Sights? Sounds? Beer? Culture? I can point you in a direction if I know what you are after...
You can choose multiple maps to cache, including Google maps. Cache Tokyo at any desired level before going or at your hotel and have fun
Use maps less :)
There is an alternative, though not as functional: Wear Maps Gps info
I also use Wear Task manager to kill maps from the memory after use just for safety...
BTW Wear Battery Info itself is known to impact battery life