Yep, lots of info about this around:
http://en.wikipedia.org/wiki/Wood_gas_generator
http://www.woodgas.net/files/FOA%2072.pdf
The good thing about it is that the vehicle's engine doesn't need to be modified much, as long as the gas generator is set up right. IMO, a lot of locations would use these for power generation, light industry and possibly transport. Also very likely for rear-area military vehicles.