When daughter was young...from age about 3 onwards she was very poorly in the car. It helped if she was sat in the front to ensure she was always facing forward (its the glimpsing stuff flashing past that causes a lot of the problem). However, what helped the most and usually ensured that even a long journey stayed vomit free was, have her listen to a story tape on a personal stereo. Technology has moved on a pace but am sure the modern equivalent would have same effect. She would sit there chucking to anything really rude by Roald Dahl, or Dick King Smith's lovely animal stories. When she was old enough to 'believe' we also introduced her to the acupressure wrist bands. They seemed to calm her down , the whole process of getting them out of the little box, positioning them carefully seemed to take effect. I am still not sure how they work but she believed in them, so we carried on using them until she was in her teens..