Hello,
While it is not possible to send the alert while the device is in "Failover" mode, it is possible to send an alert when the mobile connection changes to a disconnected/connected state. This can be done by selecting the device in question, selecting the Alerts drop-down menu, and clicking the Create Alert button. Then select the Alert event as Mobile data and specify the rest of the parameters as you wish.
More alert types are planned to be added in future releases of RMS.
Best regards,
DaumantasG