Not sure why there is one one-star rating. I’ve used the app for several years. The big plus is that it allows email and text communication (outgoing) for nearly anybody using the phone (limits on the YB3 by itself are substantial). Having had the device in a backpack and been in a tent with phone, it was nice that the Bluetooth connection carries a fair distance. Setting everything up is mildly clunky, but once done all is good. Can control tracking pretty cleanly. You do need phone online for setting up some parameters (eg to use twitter or Facebook from YB3). For its purpose, it works just fine.