This app works with Rtrivr key finder, which can be ordered at http://www.rtrivr.com
Supported Android Devices using 4.4 or higher (KitKat or Lollipop):
Samsung Galaxy S4, 5, 6
Samsung Note 3, 4
Nexus 4, 5, 6
HTC One M8
LG G3, G4
Mi Mi3,Mi4

If your device is not on this list but uses Android 4.4 and Bluetooth 4.0, there is a good chance Rtrivr key finded will work fine, but we are not able to offer the same level of support in troubleshooting scenarios.