After creating a 'doodle pad' you can just send the URL to partners. [example] If you are working at the same time, you will actually see it happening in real time. Pads can also be embedded in a website.
Tip: Higher math teachers who are teaching how to solve difficult problems, use Sneffel. Create a step by step demo of how to solve. Embed it on a page or in a blog. Students can then go to it and hit the 'replay' button to see the steps worked out.