A friend of mine (who doesn't ride) heard about these and gave me some info on it. I've considered picking one up. End of the season last year, I had a close brush with an SUV. The guy's mirror hit me in the arm as he passed me under a narrow viaduct. Thankfully, I stayed on two wheels and didn't stray too far off course (I attribute that to the mountain biking). I came away with no injuries, but it was an eye opener.