Just dip the Rotgutonix pen into a glass of alcohol (no mixers, please), and let it soak for 20 seconds. The pen's liquid-crystal display will tell you if you're about to drink some real whiskey or some nasty rotgut, it'll tell you.
Unfortunately the device can currently only detect the chemical composition of 6 brands of liquor: Johnnie Walker, JB, DYC, Havana Club, Pampero and Brugal....The good news is that makers of the Rotgutonix are working on a future update that should allow it to detect up to 20 different booze profiles.
You know, there's any easy way to get around the need for a Rotgutonix detector. It's called ALWAYS ORDERING THE CHEAPEST BOOZE POSSIBLE. Any funny switch-o change-o business works out in your favor! Well, provided they're not just watering the alcohol down. Which, FYI, is grounds to stab a barkeep with a little plastic sword or umbrella. YES I DRINK FRUITY DRINKS, WHAT?!
Hit the jump for one more shot.