Personally i do create other locations like one for mobile devices. The locations should be for broadcast networks and with a network probe etc when you need to connect to machines or manage them a site master makes things happen quicker. The mobile devices location i set not to do the off line monitoring.
If you still want them all grouped then create a custom network monitor to run on another server to connect back to that location.
You would of course also get lots of off line server alerts if they are managed.