Methods and apparatus for accessing and monitoring the gastrointestinal tract are described herein. One variation of a feeding tube system may generally comprise a gastric access device having a length, a controller in communication with the gastric access device, and one or more impedance or conductivity sensors positioned along the length and one or more temperature sensors positioned along the length. The controller may be configured to receive a first signal associated with the impedance or conductivity sensors and a second signal associated with respiration and determine whether a placement of the gastric access device is within a stomach of the subject.