The investigators aim is to evaluate an instrument for supporting physical activity and monitors multiple parameters of frailty (a pre-disability condition) in frail elderly persons. The investigators are therefore developing a smart shoe insole to monitor key parameters of frailty during subject daily life and to promote walking. Our primary aim is to assess the acceptability of the solution for the follow up and the motivational coaching of frail patients at home. Results from this study will also be used to elaborate the design of a further larger national multicenter randomized control trial assessing the efficacy of the solution to prevent disability.