What would you like to see from Frictional next?

[Bek]

but ONLY if you and your partner are within a certain range of each other (earshot).

There's a VOIP program called Mumble that does this part already, of course it needs integration with the game but it's still pretty cool.

As for the rest of the idea, I think it's a cool beginning idea, and I'm sure something like that has potential if the basics were figured out. Trouble is all co op games need a single player part for when you're buddies are offline.