The Philips iPill determines its location in the intestinal tract by measuring the local acidity of its environment. Distinct areas of the intestinal tract have distinct pH (a measure of acidity) profiles: the stomach is highly acidic and upon exiting the stomach the acidity of the gut sharply decreases and then becomes progressively less acidic from the upper intestine onwards. Armed with this pH information and data about capsule transit times, the location in the gut can be determined with good accuracy. The iPill releases medicine from its drug reservoir via a microprocessor controlled pump, allowing accurate programmable drug delivery. In addition, the capsule is designed to measure local temperature, and report measurements wirelessly to an external receiver unit
