Not through Address Book, but if a contact has no compatible contact methods their name should appear red in the "To:" field:
The drop down on a persons name will give a breakdown of contact methods, the blue iMessage icon denoting that that address/phone number can receive iMessages. If you manually choose an incompatible address or phone number their name will be highlighted in red.
Note that there seems to be a bug where if you close Messages when someones name is highlighted red when you reload Messages the next messages to that person will still be sent to the incompatible email but their name will be highlighted blue - it's only Beta software after all.