I’ve downloaded a few ski related apps myself, eg GPS one that gives your speed etc (although in reality never use it at it a) costs a fortune to use abroad and b) soaks up battery), snow report one ......
I guess that if I was looking for a ski destination/holiday I would use a PC or laptop rather than the iPhone. Whilst I love the iPhone it’s limitation I suppose is its size. That said I think a WTSS app is a great idea.
Things I like from other apps include - link to resort website/webcam, up to date snow report, piste maps etc. The Austrian Tourist board launched quite a good one recently - iSki Austria. iTrailMap is another good one.
Would it be feesable to have the book as an app as a separate app?
That’s my tuppenceworth anyway and good luck with the project.