Scientists in Israel at Tel Aviv University have developed a sensor that can detect two of the three most common date rape drugs: 1) GHB (gamma-hydroxybutyric acid) and 2) ketamine. A benzodiazepine called flunitrazepam, aka Rohypnol (known as roofies), cannot as of yet be detected by this new sensor.
Production of GHB is relatively inexpensive. GHB is colorless, tasteless, and odorless and readily dissolves in liquid. A deadly dose is 2.5 grams. Ketamine is commonly used by veterinaries and pediatrics as tranquilizers. Rohypnol, part of the Valium family, is a prescription drug and can be really dangerous when taken with alcohol.
Drugging a drink will slightly change the optical properties of the drink. An optical sensor will detect this change. The chemists are still trying to determine exactly how they want the detector to function. Being discreet is high on the list so that the sensor can be used by a woman at a bar to check her drink.