In this work, a novel low-cost and portable Internet-of-Things (IoT) reader for the measurement of passive electromagnetic wireless sensors is proposed. This reader is used to interrogate the sensor within a short-range wireless link which is useful for the remote monitoring of harmful substances. This remote monitoring is possible thanks to the inclusion of the IoT functionalities. The proposed IoT reader is based on four layers (the radiating layer, the RF interface, the IoT mini-computer and the power unit) which are described in this communication. In order to show the validity of the system a demonstrator including all the layers is manufactured. Furthermore, the demonstrator is tested with different liquids and it has been demonstrated that a linear approximation canbe extracted from the reader measurements.