I am using an FMB92,0 which is set up with an Airtel M2M sim card.
It is configured to use Accelerometer as Movement and Ignition source and Deepsleep after 2 mins of inactivity.
Some times the FMB920 stops sending data to server, and its not the battery is low, as after connecting to a computer via Bluetooth reveals the SIM card is deactivated, but as soon as I reboot the device, it starts sending the data again.