Thanks, @tomcarpenter, glad you are interested in the subject.
About medical protection, it depends on your home base country. In my case, I am a french citizen and declare my revenues in France as a freelancer, so I am covered there and got a long-term travel insurance.
If you can manage your business with a phone, wifi connection and a computer, it is totally possible to do it on the road. You just have to considerate the time zone to be able to reach your clients on time. Wifi was really good in most of the countries I visited, and if you need a quiet/working environment, you can find co-working place easily where they can provide you private desk, print, high-speed wifi... and other digital nomads to meet.
I hope I answered your questions. Feel free to contact us if you have more questions :)
RE: How to become a Digital Nomad?