The app requires a Bluetooth reminder device "RU Taiwan", an edition for Taiwan tourism theme; it runs in the background and provides a timely alert when you about to leave behind your stuff. If you happen to miss the sound alert at the time when you were away from it, with iPhone’s realtime GPS location service, the app can track the last location of the disconnection and help you retrieve the device.
Continued use of GPS running in the background can dramatically decrease battery life.