The SDK supports offline modes and allows openings via Bluetooth. UnitController.getUnits (Api) will give you nearby units that has been cached.
Even in offline mode Bluetooth and Location must be enabled!
Network / IP based openings will not work in offline mode!
If the app gets killed and you restart it, all should work fine being in offline mode.
You will normally initialize the SDK.
Once the app started, you need to check for UserManager.Status (Api). Just wait until it becomes Ready.