I love the idea of the smart phone app as an affordable navigation tool. Even better (maybe a future feature) would be if it could take the new "enduro" roll chart format from Rally Navigator, and display the roadbook too!
BUT, at least with the coming Diabolical Rally, smart phones, iPads, and similar devices will not be allowed for any aspect of navigation. That's the case with Dakar too. The reason is it's too easy to use these devices to cheat. I can think of all kinds of ways to use a smart phone app to gain unfair advantage over other competitors. And I know if it's not clearly stated in the rules, someone will eventually outsmart everyone and use an electronic device to do what nobody else can do. As a race organizer, one of my jobs is to try to keep everyone on a level playing field, and keep the challenge high. And I'm super motivated to uphold the challenges that difficult navigation present. The more we let "smart" electronics into rally navigation, the more an essential part of rally is lost.
The one element of this that I'm still in favor of is if such a device was very limited in its capabilities, and were controlled and handed out by the race organization (like they do at Dakar with the special GPS unit). In that way, everyone would be assured of having the same basic tools and nobody would have advanced devices that take the challenge away from rally navigation.
I also think it could be great for those just coming into rally. As an affordable tool for practicing on "play" routes it seems perfect!