I was thinking about this thread today and decided to experiment. I found a way to do it through one of the apps on my phone which is a paid app: 'Better Cut.' I imagine it's also do-able through 'Any Cut' which is the free version of this app. It's probably just a matter of time before someone realizes this functionality is not there and makes an app specific for it.
In the meantime with Better Cut (or possibly Any Cut) installed:
Long press on the home screen.
Choose 'Shortcuts'
Choose 'Better Cut' (Or Any Cut if that's the case)
Choose 'Activity'
Select 'Data Call Settings'
Select an Icon, choose a name and select 'Create'
Then open the shortcut and it appears to take you to a menu that might be normally only accessible through some uber secret technician master code of awesome powerfullness.
But yeah... just uncheck 'Data Call Enabled' and that will cut off all data communication.
Hope this helps...
EDIT: Confirmed SMS works too with it disabled.