I'd like to be able to be notified the next time someone comes online and optionally have a message delivered to them when they come online.

We have employees all over the world, so sometimes I want to ask someone a question or let them know something, but it's not urgent enough to @notify them and have them get notified immediately, especially when it's 3am for them. Currently right now I have to jot down my question so I remember it and then check Hipchat periodically to see if they're online.

It would be super useful if I could, at minimum, get a notification when they sign online and ideally pre-compose a message to them to be delivered when they sign online.