Hi, I'm new to the forum. I created a liquid container that holds both gatorade and vodka separately. It has an arduino micro controller with a relay to a 12v solenoid. The solenoid controls a valve to the part of the container with the vodka. The arduino is also attached to an NFC shield (Seeedstudio's shield) with a u.FL connector for the antenna.
The antenna is placed on the side of the container.
Basically, when I hold the container, the NFC ring allows me to get both Gatorade and Vodka from the straw. When anyone else holds the container, only Gatorade will draw through the straw.
It's essentially a selective flask. The straw is fitted to a Y-pipe and the solenoid allows vodka flow into the main pipe that always draws gatorade.
It's in prototype form right now, so the electronics and packaging are much larger than they need to be, but it is simply a proof of concept. The largest and bulkiest pieces are the 12 volt power supply and solenoid itself. The electronics could be optimized on a single printed circuit board and made very small... I think around matchbook-sized. All-in-all, I believe the electronics could be fit into something the size of a hockey puck or thereabouts. Then all you would have to do is get a double-stacked container that had internal passages for plumbing.
It would be much easier with a 3D Printer, but mine hasn't come in yet, so Version 2.0 to come in the future.