According to Fosspatents on blogspot.com, one of BT's claims includes: "Following a login or the transmission of an authentication token, Google "offers the list of items that the user is entitled to access", and retrieves any such items at the user's request." Doesn't that pretty much cover *any* web server where you login to gain access to whatever your account entitles you?
I like Hobbit/Xymon too. I had it running for about 8 years quite happily on an old DL380, single 733MHz cpu, 512Mb memory. I think the peak traffic it took was about 3500 status messages for 500 hosts. Almost all the messages were generated by scripts running on the server, grabbing web pages from all those hosts.