My buddy and I use the cheap Motocomm system which can be used with the FRS radios. You know the ones, the Motorola or Midland family walkie talkie style radios. We started using them on ATV trips to warn each other about hazards and turns when we were spread out from dust. We decided to use them for MC rides because my buddy would miss turns and it would take me miles to get his attention to turn around. The radios work well below 75mph, but wind noise makes it hard to hear everything above that. You can, like someone else said hear enough to slow down if you need to hear better. For $50 for the system plus another $35 if you want to incorporate your music into the system, it was a good way for us to go.
Rick