I have to drive on a highway to get to my neighborhood and there are lots of bicyclists riding up and down the road who have on headphones and are rather oblivious to the cars whipping by at 70mph. I would think a better option for bicyclists rather than blocking off their hearing would be something like the new gear from Korean firm S&J.
The company has unveiled its new products that will be shown off at CeBIT next month called the Eggy and the Bike Speaker. The Bike Speaker is just what it sounds like, a speaker that mounts to the handlebars of a bike. The speaker has a built-in micro-mini 20mm driver and 2W digital amp. The speaker also has a FM tuner, volume control, watch, and some models have a stopwatch function.
The Bike Speaker is removable from the bike for portable use as well. The Eggy is an egg shaped portable speaker sharing the same micro-mini 20mm driver and 2W digital amp. Eggy connects to a USB plug for power and plays music from your computer.