I used to work for a company called ihiji (see ihiji.com) that specialized in providing a remote monitoring interface for Crestron, AMX, Control4, etc....

Those systems were all pretty good at the local management side of the house, at least for the modules they had. But they never had any clue about remote monitoring and management.

We spent a lot of time working out the protocols for those systems so that we could appear to be a local standard node on their network, in order to provide that remote interface. It was a major royal pain.

But I did get a good invited talk out of the experience, and I still think that project was the closest I ever got to doing anything really cool.