sb_status is a bit like status and outputs the steamids of clients into console. It is required by steambans to submit a demo for banning. If you decide to add support for it I can test it on my home computer even to see that it works. I have local copies of all of my servers that I use for testing. They do connect to steambans when I run them so it is possible for me to see that it records the data correctly and is up to the standards of steambans.
And yes if someone is watching the demo the outputs should show up in console.
Hopefully with a great tool like this we can finally put every hacker in his place
Also rather than try to limit the size you could force it to start a new demo every x min. If you figure that every min of demo is about 2mb than you could translate it that way.
edit: oh I had a great idea for a long term update! Ability to auto compress demos older than X.