Thanks for all the help everyone, and to V-fib: I had not heard about the one you are describing, but I will be sure to look for this one as well. Thanks for alerting me to other options. The one that I was looking at was about 3-4 inches long in a cone shape so that no matter the barrel diameter it would always center itself.
The pistol that I was looking at was a Kimber Custom Covert II which has a laser sight built into the grip. I figured that I could use the laser boresight on the wall and just match up the two laser dots by adjusting the one on the grip. I know it will never be perfect but does that sound like a reasonable way to do this? Thanks again for everyone's input!!