Kind of a neat idea, but unnecessary.

If you have rim brakes, you can either use your brakes as guides, or put your thumb on the brakes and feel the wheel movement.

I've used one hand to hold something against the wheel. Not the quickest maybe, but simple. A bic razor handle sings when it hits the rim.

There have been pictures of people using popsicle sticks and rubber bands to do the same thing. You might as well start your repair with a refreshment.

Removing the tire may aid with analyzing the hop.