Originally Posted by JohnJ80

I've spent a lot of time working on just this problem and it's actually quite tough to solve. There really aren't any easy high quality solutions.

The best intercom solution is the Terrano Systems stuff. We used the first version for years and upgraded to the new version this year. The noise cancelling is great, it's full duplex. We primarily use it for the two of us but it is also supposed to work with a total of 4 units but we've never done that. Range is about 0.5 to about 1 mile. The more line of sight it is the better it is. For the two of us riding, this is excellent which you would expect based on the price. We have been using their stuff since it first showed up as Cardo System (now spun off as the cycling stuff into Terrano Systems).[..]