Blow Me is a company in the UK that will setup at your event and alcohol breath test everyone before they get into their cars to drive away.
They use Draegar 6510 breathalyzer, the same one used by police forces across the UK.
They are mostly booked the morning after cooperate events, after employees and clients have have time to sleep off their drunkenness in hotels. According to the company, at a recent even of 300, 74 said they felt hungover, but ok to drive the next morning. Turns out that after testing, 30% of the 74 were still over the legal limit at 9 AM!
I’m sure that this model is replicable in the US and around the world.