In my limited experience.
The speeds will be approximate, and no one is going to take uncalibrated readings seriously. Then they we beat you up about how do you "calibrate it". Which is nothing more the using a calibrated tuning fork to verify speed.
You could use a Sportster III with display, and video record the LED sign. I did this for a while.
I use radar myself accurate to +/- digit.
The other thing I learned as you can't judge speed accurately and no one will do a thing about speeding below 35 mph.
Interesting software, thanks for the link. check out the small print "**" accuracy says "depending on camera". I don't know how they would calculate distance to any accuracy?
For $130 bucks might be interesting to play with.
This maybe too much for you but check it out.
My setup
Good Luck!!!