The Microsoft Kinect camera and associated sdk has been validated as a tool for postural and balance assessment in peer reviewed scientific literature (8,9). It has shown reliability in measurement and inter-reliability in assessment and re-assessment. A study by Yeung et. al compared the accuracy in postural sway between the Vicon system, force plate and the Kinect SDK for four different balance assessments including  Standing eyes open,  Standing eyes closed,  Standing eyes open on foam, and  Standing eyes closed on foam.
The results of this test found that the Kinect SDK was comparable in accuracy to both the Vicon system and force plate analysis of body sway in all 4 of the positions listed above. According to this study “Overall, Kinect is a cost-effective alternative to a motion capture and force plate system for clinical assessment of TBCM sway (8)”.
“To conclude, this study compared three TBCM sway assessment tools: a Kinect system, a motion capture system, and a force plate. The Kinect system demonstrated comparable intra-session reliability and accuracy in TBCM sway measurements to the motion capture system and the force plate. The Kinect and Vicon systems demonstrated comparable reliability (in terms of ICC2,1 and CV) and were sensitive to different tasks (EOn, EOf, ECn, ECf) (8).”
A study by Clark et.al found that the Kinect SDK provides “the ability to differentiate postural control strategies using an inexpensive, portable and widely available system could provide clinical and research benefits in a variety of patient populations. Our results suggest that the Microsoft Kinect provides anatomical landmark displacement and trunk angle data which possesses excellent concurrent validity when compared to data obtained from a 3D camera-based motion analysis system (9).”