The app comes with a lot of nifty features you won't have access to otherwise. You will be able to:
See available bikes and locks in the area.
Unlock bikes when you are close to a station,
See the duration of your trip
Get a confirmation when your bike is parked.
Report a bike as broken after the ride, read more here.
Get notified before extended rental start running, and see the cost.
See how many trips you have in total, and how many stations you have visited