I have the Precision Trolling App on my iPhone and use it all the time. It is very easy to use. You can purchase as many lures as you want for $1.99 each or you can purchase all of version 1 for $49.99, or the lifetime package with future updates for $99.99.
You are correct that the hard version is out of print, and I doubt you can find a used copy for 100 bucks.

Hope that helps,
Gradyfish