Amy and I use a set of Cobra radios, they havea pretty good holster that clips to your waist and a VOX (no button pushing to talk) head set and mic. Careful of the headset type, it has to fit inside your helmet. We have had the same ones for two years ( we lost the set before that) and they work well ( 2 mile range) and cost a LOT less then the clip to your helmet Chatter Box things. We got the one we have now because they are btight yellow... so we don't use another set. :)
Before the radio I was always turning around and looking for Amy. Now I just say hi and when she yells back, then I turn arround.