connecting several devices through wifi or bluetooth should allow:

1.   one-click navdata update transfer & flightplan data & wx data & notam data transfer from one device to another (think one device connected in the hotel and updated the night before, the other without internet installed in a plane)
2.   one-click download of log files / breadcrumbs / history data from primary/master device. the reverse of the navdata update so that any recorded history / stored flightplans etc... may be downloaded to a second device for post-flight analysis, e.g. in a hotel during a flying holiday.
3. editing a flightplan/changing active legs on one device should synchronize with the other device in realtime. also offer e.g. an onscreen keyboard.
4. if a really good gps/traffic info source is available on the fixed install device, that data feed should be made available to the secondary device.