You could improve on the paper towel tube idea. Get a funnel, a couple feeds of plastic hose, duc-tape it to the small end of the funnel, get a towel and duc-tape it to the other end of the hose. Drill a couple of holes in the rim of the funnel, get some elastic, strap the funnel over your ear. Use the dowel to aim the far end of the hose at this thing or that as you pedal down the road.
It could work.
For maximum fun, ride by your boss's house on lawn-mowing day while using this homemade stethoscope.
Not making fun of the paper towel tube. It's a good idea. I'm just having a brainstorm brought on my a couple beers.
