I posted a thread on this but realised that popping it here might be a better idea as I have found this app so useful.
I have been using this App for a couple of years but a recent update added a host of new features and I am unaware of any app offering such specific motor homing features. I reviewed it on my blog here and have also uploaded a pdf of the review.
It's available in a Free Lite version and a paid version. I have no connection with them other than they asked me to do some unpaid beta testing before the latest release. iOS only.