Bike-mounted commuters can do that "I'm so busy, I need to call while I'm driving" crap, too. Heck, they can even do it so that everybody within the vicinity hears their conversation. As long as they have this: the Bicycle Speakerphone. Take that, busy executives driving fancy cars.
Just like any regular wireless speakerphone unit, it connects with your handset over Bluetooth, giving you the magical powers of piping audio from your phone into the speakers. Unlike them, however, it's meant to secure right on your bicycle's handlebars, giving cyclists like you even more ways to irritate nearby pedestrians. Yay!