Ryan's profile contains fake pictures of him allowing him to check in and see who's in there without exposing himself.
Ryan notices one of the single women that checked in and proceeds to watch her all night as she gets dangerously intoxicated.
Ryan follows her and makes his move.
This part is not enabled or disabled by a dating app. Ryan can do the same thing by hanging around bars and following their patrons around. I do think, though, that the problem is that some men seem to develop unhealthy obsessions with pictures of women they haven't yet met, and that stalkers will definitely spring from this app if it gains traction.
Specially, Ryan might view the interaction he had, despite being under false pretense, as a legitimate personal connection to the individual. i.e. the online checkin might be a trigger for stalking behavior that simply being in the same physical presence might not be.
I mean, maybe this isn't a big deal. But I do think it could potentially be different.