That is a good idea for a lot of reasons. It would be a platform that could be built out to incorporate drug sales too since a lot of times someone might want to buy weed in a city they are visiting but not want to root around the streets or the internet trying to find a source. So, there is a lot of potential. I think you should do all of the transactions in bitcoin though, giving the fact that transaction processing is going to be a huge hassle. I can't believe Uber is able to process transactions at all given the illegal nature of what they are doing in most cities.