Alright well how do I hand the marker to a coworker so they can append to my image? Do I need to set up a projector or something?

Forget the fact that I don't have the space for a whiteboard in my home to begin with...

Excellent questions and astute predictions of what's in store on the roadmap. :)

Very soon we will be adding viewer annotations (ability for remote viewers to add content/comments on your board). As you're facing your laptop during your remote presentation anyway, we've found that this works reasonably well. The augmented reality approach (via smart glasses or synchronized projectors) is also on the map but getting the timing right is much trickier. The UX of it is nothing short of magic but the market for people with glasses or synchronized projectors is fragmented.

As for your last note: you don't need a whiteboard! Flipcharts or electrostatic sheets are cost/space-effective alternatives. Also, you can simply point your camera at your notebook and scribble away. Indeed, many of us do this, it's very natural (though, admittedly, we're still getting some kinks out).