I'm quite happy with SnagIt - just take a screenshot of my starting position and start to annotate it. Or start with a blank image in SnagIt and start to draw my boxes and arrows.

I find my boogie board works really well as an input device! I believe you can also set it up to transmit to a webpage.

I use the free edition of Autodesk's SketchBook pro, with a Wacom tablet. This is for teaching, not remote work.

Realtime Board is pretty good: https://realtimeboard.com

We've used it a few times with good success.