Hi Henrik
Growl is almost like peer-2-peer where anybody who has Growl installed can route 'Growls' to other users, whether on an internal LAN, or over a WAN. Individual users can also 'Subscribe' to notifications from other workstations. Notifications can also be forwarded to Email, iPhone or Windows phone.
I was just thinking of having the ability to pass notifications to different workstations, particularly on a local LAN (but Mobile would be good as well). From what I can see, "Whatsapp" is good for smart phones, but there is no MS Windows client?
Hope that helps?
Cheers
Andy