Was in NY last week. Caught a cab (one of 200) with a touchscreen monitor behind the driver's seat. The driver told me that it was a one year test. I could check news, look at maps and search for other information wrapped in a whole lot of ads.
The taxi driver told me that the product works on the cellular network and was free for now but will cost the taxi driver once the trial period is over.
After I browsed around a bit, I was able to look at the location of the cab on a map in real time. At the end of my trip, the monitor showed my fare that I had to approve before the receipt printed.
Digital advertisements will try to grab our attention at every public place. Interesting piece from O"Reilly Radar on the topic: What Does it Mean for Public Space to go Digital?