Richard Solo's FreeWheelin audio system (US$150 street price) allows you to add stereo speakers to your bike helmet. As the picture to the right shows, it consists of three small boxes that use a high-powered variant of Velcro to mount to the helmet's back and sides.
It's about as dorky looking a product as you could imagine but dang if it doesn't deliver really fabulous sound.
I hooked up my test unit to USB power for a few hours before taking it all for a spin on my bike. Charging is really easy, but you either have to hook up your entire helmet or dismount/remount the speakers and control box from their attachment areas. It's not a big deal either way, I found. Pairing the Bluetooth was also super-easy.
The speakers sit on the outside of your helmet, so they limit interference with your normal hearing. That's an important consideration when biking in traffic. You can hear your tunes and sense the motor of the idiot driver that's about to pass you and then turn to the right directly in front of you (This is entirely a theoretical example).
Many cyclists avoid ear-based audio entirely or use one-eared speakers, but FreeWheelin delivers a full stereo experience. Moreover, the sound surrounds your ears instead of being directly aimed at your ear drum. I'm not an audiologist, but I'm guessing this is generally a safer prospect.
I made sure to test the unit in reasonably heavy traffic. I picked a road with three lanes of traffic in each direction, going at 45 MPH (posted speed limit) at about 7:00 PM -- when rush hour has finished but road use remains high. I rode the adjacent bike path , which is essentially a city-purposed sidewalk. To make things really difficult, I put on an Audio Book, the best test of listening clarity.
As expected, there were occasional times when I couldn't distinguish sounds mostly because there were a lot of loud, busy cars out there, but overall I had little trouble listening to my book. During a quarter hour of biking along that stretch, I could easily follow the story and missed very little audio. The sound quality was excellent.
It's when I turned off the main road and started a quieter trip home that I encountered the flip side of my helmet sounds. It wasn't about the external noise I could hear through, it was about the noise my helmet itself was generating.
In some ways, my helmet became the cycling equivalent of one of those cars blasting their speakers along the road. Although directed in towards the skull, the audio bounces off and is clearly audible a number of feet away (I tested this using a spare child). It's not a huge deal, exactly, because you tend to move away from other people rather quickly when you're on a bike, but the FreeWheelin system is a bit, well, noisy for others.
The speakers were much lighter in use than I feared. I had expected them to weigh down my helmet a lot -- but after a few minutes, I really didn't notice them. There is the "dork" factor (as well as the broadcasting your audio factor) of having these boxes stuck to the side of your helmet. You'll need to decide if the benefits of the audio system outweigh the fashion faux pas.
In the end, I found FreeWheelin a really exciting product to use. It nicely balanced safety against entertainment and offered well-built high-quality design.