Kalle,
I disagree, but maybe I am only lucky with my observing spots. There are only meadows and forest and thus no farmers at night. I have never met anyone with a dog. The local hunter gets a short message before I leave and stays away. Every single person showing up in addition would make a big difference.
Holger
Hi Peter,
I think like Dirk - an app guiding persons to a recommended location far from my favourite spot would be great 
More seriously: "serious" observers (whatever this means), visual or photographic, do not want anyone to show up with the car lights on at night, or leave earlier (e.g. you also mention families as one group you are targeting - I guess they do not stay as long as I do). If one thing, I could imagine an app where I could "book" my favourite spot! Seeing in advance who's there already would also be great - and something I would not share publicly in an app, or at least only with the few people I know and would like to meet. Maybe that's something.
The "less serious" observers who don't care about dark adaption may like your app though - although I think you will not find them here, or at least not yet. Maybe that's the same group as the potential Stellina users, just a different way of doing astronomy.
Best regards
Holger
