I had to set a timer (for between 5 and 11 minutes depending on circumstances) to remind me to check Vladimir's screen (resetting the timer manually after every check). If I did not, I either spent too much time looking at his screen or let him go too long without monitoring.

I actually imagine this to be less of a problem when you have more people as you don't need to think about checking the others' screens at all a la the bystander effect. And even if people check other people's screens really rarely, just knowing that there are multiple lesswrongers who can actually catch you procrastinating should be good enough in most cases. Also a quick glance at the hangout can quickly tell you if someone is procrastinating in a really obvious way such as being on facebook, youtube etc. In addition I actually speculate that if the chat is big enough there is a reasonable chance that some people will spend a large fraction of their time in the hangout just monitoring other people. This action will not be productive at all for the observer but at least it will be beneficial for the room as a whole. (I am in no way saying that we need such observers, just that they might show up on their own).

I am not sure if it will actually work in the way that I imagine it to work and you might be right that it will be too distracting but a group chat involving screen sharing is definitely worth a try at this point.