A portable electronic device and a related methods are described using an portable electronic device, preferably with telecommunication capabilities to allow for data and/or voice communication via private or public networks, with an integrated gas sensor (12,21) sensitive to hydrogen and/or methane and/or carbon monoxide, and an opening (107) for a contactless delivery of a breath sample of a user to the sensor and elements ( configured to store a time sequence of data representative of a plurality of hydrogen and/or methane concentrations and optionally a correlation and testing unit for correlating the time sequence of concentration measurements with a time sequence of events relating to the food intake of the user and for performing tests, in particular test for food intolerances or cigarette consumption, on the correlated data.
