NextCompanion

A minimalistic client for Nextbike. Still under early development, use with
care.

The app allows you to sign-in, see a list of bikes, rent one and return it.

The app is neither official, nor feature-rich. It also doesn't allow you to.
sign-up to nextbike or to delete your account, use GPS or read the news
feed. It was just tested for Norderstedt, so it's not guaranteed to work in
all areas. Also, the app has no support for flexzones.