I came across this and thought that others might like to try it also. This program uses your cell phone as a tach that is supposed to be accurate to 1 rpm. The price is certainly right to double check your tachs once in a while with this. Go to this site (
http://www.tunelab-world.com/) and select "Downloads" and then scroll down to "Pilots Only" for the download. There is one version for your PC, and another for your phone. I've downloaded the program but haven't tried it yet. The claim is you can check the rpm of planes from up to 1/2 mile away with this.
Best,
Free Cell Phone Tach Software
Linear Mode
