I was speaking to Charis and Jarijn (Look at those first-name Twitter handles!) from Smashing Conference last week, and they left me with this real nugget of advice for anyone hosting in-person events with a hybrid / online component.
There are a lot of gaps in in-person events: gaps between talks, lunch breaks, planned networking sessions etc. If you're providing a livestream of the event, these gaps are effectively dead-air and while it might be presented simply as a break in proceedings for online viewers, Smashing offered their online participants something special: a backchannel.
During the gaps, Jarijn would connect to Vito on a separate livestream channel to the main one, using his laptop, and give folks an "on the ground" view of proceedings. This could be backstage interviews with speakers, or chats with participants, or even just a tour of what was happening in person.
This is such a simple idea, but I can imagine how special it must feel for online participants to have this perk ... a bit like having a commentary track when watching sports.