I was sceptical about travel sickness bands as well, but they worked for us.
We moved house and the road in to town is fairly windy, plus roundabouts etc. ds2 was puking every time we went anywhere.
We told him about travel sickness bands, and kept our scepticism to ourselves. And he stopped being sick overnight.
Unfortunately it only worked for about 18 months!
However, he is rarely sick nowadays, and able to give us plenty of notice these days to find somewhere to stop. He usually feels better after actually being sick and isn't too bothered by it!
A nappy sack in a large ice cream tub or similar is our preferred vomit receptacle! (As the nappy sack is leak-proof and the contents can then be easily disposed of.)
Playing a DS or reading in the car is a complete no no for him, and makes him feel ill very quickly. Looking out of the window at the horizon helps, as does keeping the car cool and plenty of fresh air, and dressing very lightly - T-shirt no jumper.
We got in-car DVD players, but I didn't think he'd be able to watch them. But to my surprise it seems to have really helped. He hasn't been sick at all when watching a DVD since we got them 18 months ago.
Sorry that's so long, hope you find something useful in there!