Biofeedback of heart rate variability (HRV) was applied to patients with diabetic polyneuropathy using a new mobile device allowing regularly scheduled self-measurements without the need of visits to a special autonomic laboratory. Prolonged generation of data over an eight-week period facilitated more precise investigation of cardiac autonomic function and assessment of positive and negative trends of HRV parameters over time. Statistical regression analyses revealed significant trends in 11 of 17 patients, while no significant differences were observed when comparing autonomic screening by short-term HRV and respiratory sinus arrhythmia at baseline and after the 8 weeks training period. Four patients showed positive trends of HRV parameters despite the expected progression of cardiac autonomic dysfunction over time. Patient compliance was above 50% in all but two patients. The results of this preliminary study indicate a good practicality of the handheld device and suggest a potential positive effect on cardiac autonomic neuropathy in patients with type 2 diabetes.