Regular moderate-intensity physical activity is strongly recommended as well in patients with type 1 diabetes mellitus. However, the more frequent complication of exercise in T1DM patients is an excessive fall of glycaemia, which remains thus the strongest barrier to physical activity and the number of difficulties patients have to meet often further discourage them. Recently, a new algorithm has been proposed, that estimates, on a patient- and situation-specific basis, the amount of supplemental carbohydrates required by diabetic patients in order to exercise under safe blood glucose levels. The present paper discusses an implementation of the ECRES algorithm aimed at smartphones, and its preliminary evaluation from the accuracy point of view versus the original implementation, as well as usability. The developed mobile application replicates the original algorithm in a portable device that, after its preliminary experimentation, may be useful to make physical activity easier for diabetic patients.