A bottle cap can do many things, if it's a Strongbow Gold Cider "StartCap." Created by Work Club, the cap that tops the cider is a RFID bottle-top that connects to a "reader" to trigger something, whether to check you in on Foursquare or even fire a cannon.
On the back-end is an antenna and a reader that connects to a power switch box to "power on" a surprise, like turning a jukebox in a bar on, for example.
At the StartCap blog, Work Club has compiled the behind-the-scenes action of how the innovative cap works, and documented their progress from day one. The agency already tested out the cap in a bar in Budapest, as well as at an event in Rome.