Interesting work by Vinay and Pavan discussing alternative approaches to quantifying dynamical regularity in human movement using approximate entropy methods suggested by Steven M. Pincus in 1991-1995, as an alternative to other parameters, including Lyapunov exponents. The advantage to ApEn methods is that they require less time-series data. This could be an interesting approach.
Just spoke with Pavan and he indicated that he would have someone send me some MatLab programs next week for me to review. Of course, these are batch processes but it may yield something interesting for real-time systems also.