In fact, other than the words 'Citizen Skywatch' themselves, the website is a barren waste-land devoid of any compelling information. But the Internet is much more investigative than that, and a prompt WHOIS search reveals that the website was registered by Take Two on the behalf of Rockstar Games. Now you're interested aren't you?
It's impossible to predict what Citizen Skywatch might refer to, but Rockstar has run ARGs pertaining to fictional in-game companies in the past. Agent or Grand Theft Auto V? We doubt we'll find out at GamesCom, but we suspect there's still an announcement on the horizon.