Idea for companion app to Pokémon Go

What if there was a companion app for Pokémon Go that helped you keep track of your distance more and hatch eggs faster?

Niantic should make a companion app where the only function is constantly tracking your distance traveled. It would let people put distance towards hatching their eggs and getting candies without the power drain of the full app. All you'd have to do is link your account with the full app on the companion app. At the end of the day you could apply your km walked to whichever eggs you'd like.

How would they make money off it? Make it $0.99 on the App Store. Most people would be more than willing to buy it since they'd be able to greatly increase their eggs hatched per day without draining their phone battery. To make it earn even more $, cap it at say 5-10km per day but charge an amount to be able to track more.

Even easier way? Take the tracking data of where people are walking frequently and sell it to businesses to help with their advertising.

How is this not a thing yet???