Usually I didn't ride alone, so there was always someone available to call.

For the times I rode alone, I let someone know where I was going and transmitted my GPS position every 15mins or so by SMS to my server, so people I wanted to know my position, could follow me on Google Maps / Earth.
In remote areas, where it had to be estimated that phone reception could be an issue, I sent additional messages with current and next intended points.
Further I had a large piece of paper in the transparent top cover of my tank bag with emergency instructions in Chinese and English.

I also attended a intensive 3 days first aid course in Europe and always carried a extended medical kit with me.
The course was besides the standard first aid, specialized for road accidents and also covered some basic medical diagnosis / treatment - almost a must for long distance travelers.

Safe riding everyone