Wearables evaluating vital parameters of human body during sports activities meet current trends of self-monitoring. Physiological parameter from sweat can improve the assessment of the body status in sports performance diagnostics for leisure and professional athletes. The presented wearable sensor device can provide insight into intra-corporal physiological processes, help to control training intensity in sports, prevent muscular overstrain, and help to improve training cycles for athletes. The fabrication and analysis of ion-selective sensors and also the integration with tailored electronics are presented. The printed sensors are developed to fit wearable devices and deliver specificity for ammonium levels in sweat.