For the tablets I was picturing things that were pretty clearly labeled - you'd know what you're getting into. Like an exhibit or an installation (but in many places, not one). I don't think I'd want people to be surprised - I'd want them to get onto the call knowing that was the only time they'd see that person.

I love that installation! My old office had a (much less elegant) setup like this that linked some of the social / kitcheny spaces across our offices and I liked it a lot.