For Wave to Unlock to work, the Orbit app runs in the background and "wakes up" when you are near an Orbit reader. If you'd rather not have the app run in the background, you can disable it, but please note that you'll need to open the Orbit app every time you unlock a door.
To disable the Orbit app background service
Open the Orbit app
Tap on You
Scroll down and tap Permissions (under Legal section)
Uncheck Enable Background Services
That's it! Orbit will no longer run in the background, but you'll need to open the Orbit app to unlock entries in the future.