A polymeric-based colorimetric gas sensor with its associated electronics targeting ammonia detectionat low-cost and low-power is presented. The gas sensitive layer was inkjet printed on a plastic foil used as an optical waveguide. The planarconfiguration of the sensor makes it compatible with large scale fabrication techniques, such as rollto-roll processes. Its power consumption and noise level were measured. The sensor exhibited a good sensitivity to ammonia with a theoretical limit of detection of 104 ppb in a constant operation mode. The power consumption was reduced to the submW range when operating in pulsed mode. It foresees applications in the field of wirelesssystems, for environmental and safety monitoring.