For what it's worth... I tried the one from Caravanners forum earlier in the year. The info for caravan parks and free camps was barely adequate but I was interested as it gave the option to plan a possible route, with maps and some info and also to record ....with connecting lines...where you'd been. I know some others do this but I wanted something simple to use that didn't challenge the iPad storage.
The other extras were journals..I didn't bother...and the option to access the journals and routes of friends or fellow travellers. That was was the first thing I disabled as I find that a bit intrusive. No doubt it has a place but not for me.
I had too many technical problems with the app as it had difficulty loading on the iPad, then tended to crash. I spent a fair bit of time in contact with the developer as I felt they needed feedback and some debugging testing.
We tried a few things then I gave up!
So....I think an app that allows you to plan and then to track your travels as well as accessing up to date info on conditions, facilities, etc along that route has potential. I know I like to have some idea of distances, potential geographical challenges such as road conditions, climbing etc and the real biggie....when you can fuel up, do the washing and find a supermarket, service centre or such would be useful.
Dump points?
The option to make notes could also be useful.
Have fun developing the ideal travel app!