an app is a lot of work. And I'm not sure what it would do over and above what a PDF of the guide does.
All it would need to be is an animation of Chris's face saying " (insert grade here)? You've got to be joking. 5+ max" It'd give a sense of the full Irish bouldering experience.
In terms of digital guides, I think pdf is the way to go. I have the Yosemite and Squamish bigwall guides on my phone (HTC sensation) and can read them fine as pdfs. You can get Adobe reader for your phone for free. Epub would be better for a kindle or other e reader type thing, but I certainly wouldn't bring a kindle to glendo!
Nice one on selling all the guides.