Backup?

My thought was that this would be a good safety/file recovery thing if I ever lost my phone or tablet. On a whim, I powered them both completely off and started AirDroid to see if I would be able to restore my files to a new device, but it can't connect with either so this isn't a valid use of the service for that purpose. Correct? Or am I missing something? Hope, hope, hope.

Many TIA for any and all responses!