A method of determining the location of an ingested capsule comprising the steps of providing an ingestible capsule having a pH sensor and a pressure sensor, having a subject ingest the capsule, recording pH measurements from the pH sensor as a function of time as the capsule moves through at least a portion of the gastrointestinal tract of the subject, recording pressure measurements from the pressure sensor as a function of time as the capsule moves through at least a portion of the gastrointestinal tract of the subject, deriving a frequency of contractions pressure pattern as a function of time and the pressure measurements, and identifying an appreciable variation in the frequency pressure pattern in substantially the same time period as an appreciable variation in the pH to determine the capsules location at a first position in the gastrointestinal tract of the subject.
