All of the bluetooth stuff mentioned above is good and well concealed, but your comms will not exceed several hundred meters. For example, would if you get separated, such as at a light.. I recommend the Chatterbox XBi... Our Rat pack uses these on our rides... GR3Wolf and I can communicate up to five miles thru the PA and WV mountains with ours... You can also pair it with bluetooth devices such as phone, Ipod and GPS...
http://chatterboxusa.com/cbxbiokit.html
Mike...