So because I'm a lazy programmer I just hijacked somebody else's presence system. The Glancing server and clients all have an AOL Instant Messaging client running inside them. When the application starts, it signs in and gets a session cookie from the server. It then uses the standard AIM buddylist to track if people have gone offline. The glancing activity is also sent over AIM. The server puts the activity level in its buddy profile and the clients check that. It's quite a nice way of sending information out to the whole group simultaneously.

For sending messages that need a response - like signing into the group, or sending an actual glance - the Glancing server runs a little webserver. Clients send messages to the webserver and receive a status code back.

Incidentally, I think this model of coupling a system which is good for presence and small groups, that's AIM, with a request-response model could be extended quite well. The group is essentially embodied in the AIM buddy the server runs, and it's persistent. It has an existence even when individual members are going on and offline. It might be fun to build more stuff that shares this infrastructure -- I'm thinking desktop equivalents to IRC bots. The same ideas as Infobot, but dealing more with problems like consensus generation software.