I think I am correct in saying that only a circular slde rule, of which the CRP1 is one type, is allowed for the nav' calc's in the PPL and IMCR exam's. You can take an electronic calculator into the exam's but not a programmable one so that's going to preclude your app'. The Whizz Wheel is a fine thing and not terribly difficult once you know how to use it. I know lots of people drop them the minute they have passed the exam's but it appeals to me being simple, sufficently accurate and not needing batteries. It also requires that you have an idea what the answer should be before you do the calculation which acts as an error check.
PS you will find plenty of threads here and on the other place telling you both that the WW is rubbish which no sane person will use one in real life and the complete opposite. You'll get the same sort of very polarised arguments when you first mention GPS as well!