I'm looking for a reliable and relatively inexpensive method for communicating with my passenger while underway.

Wireless is preferred for the sake of simplicity. I don't need to talk to other riders on other bikes, or listen to my iPod, or talk on my cell phone, or hear GPS prompts through the device - I only need the ability to converse with my passenger, who is my 7 year-old son. I've found I'd like to have the ability to check in with him from time to time regarding his comfort, and his need for food, water, restroom, and rest breaks.

My helmet is a Schuberth C3, and his is a HJC CL-Y. Bike is a 2012 R1200GSA.