This paper presents a device for breathing frequency assessment over the long period, based on low cost, wearable inertial units. Performances of the device were evaluated in static conditions on 9 healthy subjects and the estimated parameters were compared to those obtained with an already validated method (Optoelectronic Plethysmography). We obtained good correlation values (R2> 0.88) and low percentage errors (<;5%) for all the time-based parameters extracted.