Hand and arm signals only work when you see, and understand the signal, and have time to react. Communicators work even around blind curves, and cut out the mystery of the unknown hand-signal.
All motorcycle communicator radios are based off the Family Radio System FRS, except the option on the Gold Wing, which has CB. With FRS radios, you can communicate with anyone in range, and on the same channel and sub-channel. You could use your motorcycle radio to speak with a handheld radio in a trail vehicle or in the pits at the track.
Chatterbox makes several radios that have various features:
1. Driver to Passenger intercom. This just an intercom system from the driver to passenger on the motorcycle. Some of these intercoms have inputs for radio. Nonetheless, an intercom system can not be used to talk from one driver of one motorcycle to another driver of another motorcycle. Average cost $50 and up, depending on inputs and if it has a built-in radio.
2. HJC-FRS: This unit is the least expensive Driver to Driver communicator. It can be used as an intercom with the purchase of a passenger headset. It has a reported range of up to 2 miles. These do not have many channels to operate on; most do not have any subchannels, which is not a big deal if you're not in a congested area where many people use the FRS radios. Subchannels are handy when attending big biker events or on track days when many users are on the same frequencies. This unit can usually be purchased for approx. $150
3. FRSx2: This is an investment of approx. $230, but since I have purchased my 2 sets, I don't think I'll ever ride without a communicator. My wife and I can ride seperate bikes, and talk to eachother up to a reported 2 mile range. We don't normally get further than 2 blocks apart from eachother. With this radio, you get intercom with a passenger (if you wish) and communications between driver to driver or your passenger to the anyone (driver or pass) on another FRS. There is an input jack for Cell phones so you can answer your calls without taking off your helmet (not recommended for use while riding) OR use this jack with any audio alert system on radar detectors. An audio jack allows you to input a AM/FM/CD/MP3 radio of your choice. The audio cord is $10. You listen to your music, and when someone talks to you, your music is muted so you can hear them; they do not hear your music. The only person that can hear your music is your passenger that has a headset plugged directly into your communicator. Passenger headsets are normally $25 to $35. The last plug is for an optional (included) Push To Talk (PTT) button, in case you don't want to use the Voice Activated (VOX) feature. When using VOX in a noisy environment, such as on a motorcycle with loud exhaust, your mic will turn on when you don't want it to. The radio has a sensitivity dial to help adjust the microphone sensitivity.
4. FRSx1 has the same features as the x2 except it has a reported range of up to 5 miles. These units vary in price, but average to be $270 and up.
Mounting: These radios can be mounted to the side of the helmet or to the motorcycle. If you use it for passengers a lot, you may want to mount the radio in a tankbag or saddlebag. Passengers that move around a lot or tend to get off the motorcycle fast without thinking may forget that you have the radio on the side of your helmet, and their cords are pulling at your head. If you use the optional 12volt cord input, audio input, and passenger headset input, you may want to mount the radio also, because there will be a lot of wires running to your helmet, vs just one wire for your helmet extension.
Rechargeable batteries: rechargeable batteries in the radio set is nice, as long as you remember to charge it before use. Unfortunately, you can't just pop out the rechargeable battery, and place a standard AA or AA set in. I purchased the 12volt cords, cut off the battery connector ends, and added a SAE plug that plugs into my trickle charger connector. I also made a cord that has a cigarette lighter male end, so I can plug the radios into the truck to recharge. Since I have a 12v auxillary port in my camper, I can also recharge them there.
....read the full guide with pics here