[MerelyMortal]

> the app is free

I think I found your answer. Even then, paid apps/services still do that too.

In the Play Store, it just says it collects User ID, App Interactions, and Diagnostics, all for Analytical purposes. It doesn't seem like it collects location data.

I don't know if they really need User ID rather than some kind of instance indentifier, that's the only somewhat-shady thing I see.

[sneak]

Client IP is city level geolocation. When correlated with user ID and timestamp it gives city level travel history.

Collect enough points and it uniquely identifies a user.