In general, the invention is directed to systems and methods for monitoring the gastrointestinal system of a patient. In one embodiment, the invention includes techniques for monitoring the emptying of the patient's stomach. The techniques may employ glucose monitoring, pH monitoring with a consumable sensor, of monitoring the position of a consumable sensor as it exits the stomach. Consumable sensors may be employed to sense conditions, such as temperature or bile concentration, in other segments of the gastrointestinal system. The invention also includes systems for tracking the position of one or more consumable sensors as the sensors transit the gastrointestinal system, and monitoring the conditions sensed by the sensors.