The Garmin Connect Mobile app is currently compatible with select Bluetooth and Bluetooth Smart (BLE) devices only. A full list of the devices supported is available along with compatible phones here.
Many of our users have asked about Garmin Connect Mobile support for our ANT+ enabled Fitness devices, such as the Forerunner 910XT, 405, etc.
Unfortunately, due to the limited official support of ANT+ on Android smartphones, these devices will not be supported at this time.
For suggestions and comments, please see the following thread: Garmin Connect Mobile Ideas and Suggestions.