I thought of the same thing... I was going to use a pair of my old stereo headphones.... the one that cover your entire ear. I thought this would be the best solution being that when i listen to my ipod while riding with the "bud" earphones, its difficult to hear anything above 60mph, and they hurt like a bitch after i take off my helmet. So i thought i'd start with a slightly-oversized helmet and cut some pockets in the lining for the headphones to fit... You'd want to find headphones that aren't bulky, dj style, and instead slimmer so they take up as little room as possible. use the headphone jack to plug into whatever device you're planning on using for the 2way comm.... i'd probably hook it up to my nextel since that has 2 way already and use one of those cheap mics u can buy at radio shack..... just an idea
there is a company who makes a kit for the frs radio's, the kit runs about 100$ and comes with throat mics like the military uses "no back ground noise" i saw these at the laguna seca race... they work great ill try to get more info for you guys...
get a set of cusotm ear buds made, you can wear these extended, their cost varries with sound quality. regardless of cost, the sound quality will be better than expected tho because they fit way far in the ear. because of this they are also efficient, lots of sound for only milla watts.
i am at a loss for the microphone choice because of the large background noise situation. i have seen microphones incorperated into the ear buds or that mount between the helmet inside and the top of ones head.
maan just go buy a chatter box and mount it on your arm. Or you can cut out some cushion in your helmet the size of regular ear phones, taylor the seams so you dont get a shabby helmet in months and your straight. IPOD.
And last resort. Go buy a pair of "OAKLEY :THUMP" glasses.