Clinical evaluation of frailty in the elderly is the first step to decide the degree of assistance they require. This evaluation is usually performed once and for all by filling standard forms with macro-information about standing and walking abilities. Advances in robotics make it possible to turn a standard assistance device into an augmented device. The existing tests could then be enriched by a new set of daily measured criteria derived from the daily use of standard assistance devices. This paper surveys existing Smart Walker to figure out whether they can be used for gait monitoring and frailty evaluation, focusing on the user-system interaction. Biomechanical gait analysis methods are presented and compared to robotics system designs, to highlight their convergences and differences. On the one hand, monitoring devices try to estimate accurately biomechanical features, whereas, on the other hand, walking assistance and fall prevention do not systematically rely on an accurate human model and prefer heuristics on the user-robot state.