Real-time acquisition of relevant acoustic parameters in brass instruments usually requires complex measurement setups. This paper describes the operating principle as well as the preliminary design of a digital mouthpiece, which makes it possible to (i) perform, (ii) wirelessly transfer to a mobile device, and (iii) process and display measured signals, in a non-intrusive manner. The digital mouthpiece is based on a standard mouthpiece equipped with several microelectronic components and sensors. It enables the measurement, while playing, of the separate forces exerted by the upper and lower lips on the mouthpiece and of the upstream and downstream pressure. The system also includes a microphone that records the radiated pressure. Based on the measured data, it is possible to identify and analyze correlations between the applied lip forces, the measured pressures and the radiated sound. In this paper, we also present the first experimental results obtained with the digital mouthpiece, in the frame of test runs conducted with musicians from the Gustav Mahler University (Austria). The authors benefited from numerous discussions and generous advice from Prof. Joël Gilbert, in the design phase of the device. They wish to pay tribute to Prof. Gilbert, and thank him for his guidance and support.