Don’t think “shared whiteboard”, think “shared drawing space”. (It may still get called a whiteboard for marketing purposes but it won’t use an actual whiteboard.) The hardware for the physical meeting already exists: Microsoft’s Surface Hub. The missing link so far is a collaborative drawing program (I haven’t seen one, and it appears that Microsoft has tested such a feature but it’s not currently available) but it should be possible. People at home could use their tablets as a second screen to participate; I’m sure Microsoft would love to sell them something from the Surface family for the purpose.