+1A Scala rider headset which links up to mine. We talk all the time and can warn each other about cars pulling out, potholes, dogs, deer, I have to pee, I need to pull over etc etc..much cheaper than even a used saddlebag and much more enjoyable to boot. Suggest you guys look into them if you plan to ride together very often.
The Bike to Bike Comm system does an enormous amount of good for things like that. Of course, if one rider likes to listen to his radio the whole time...