Well this is pretty much a genius idea. There's a special breathalyser set up on the street in Toronto which goes all out to get you home safely. As is usual with such devices, you blow into the provided apparatus and it measures the amount of ethanol in your breath as a fairly accurate test of your general blood alcohol. And if its too high, you really shouldn't be driving buddy.
That's where the genius stuff kicks off. This booth will decide if you've had a few too many and immediately call you a ride home, thanks to the Uber car service. The app connects with a local driver and they come right along to the booth, and make sure you get home to your door safely. This first booth was set up in Toronto mostly as an advertisement of the brand, and gave away the rides for free as part of the stunt. But you can see from the video that there was a lot of interest, and people on a night out are usually pretty interested in finding out how drunk they are, making it almost a social event.
Uber is really pleased with how the test case worked and they're actively looking into rolling out the technology in other locations. If nothing else it would serve to highlight how many people really shouldn't be even considering driving home, or maybe even walking, and might help to make the roads and streets a bit safer. You can be pretty sure that the rides won't be free in the future though.