A portable device-based monitoring and security system has a docking device with a connector for connecting to a portable electronic device. The docking device has a plurality of sensors that are able to transmit to the portable electronic device signals representing measurement values acquired by the sensors. In one embodiment, the docking device is a base with a cradle and a plug connector for connecting with a jack of the portable electronic device. The base may be an externally powered unit, forming a charging station for the portable electronic device. The sensors may include a carbon monoxide sensor, an ambient light sensor, a sound sensor, a gas sensor, a smoke sensor, a motion sensor, and the like. In the case in which the docking device is a portable dongle or a protective case with a dongle, the sensors are advantageously CO sensors, TDS sensors, pH sensors, breathalyzer or UV sensors.