1. A method for detecting the location of a mobile device within an area, comprising the steps of: storing a prior location estimate for the device; determining, for each of a plurality of zones in said area, a signal-based value indicative of the likelihood of the device being located in the respective zone, based on measured wireless signal characteristics; maintaining a set of transition values, each transition value representing a likelihood of a device moving between a pair of said zones; calculating, for each of a plurality of zones in said area, a current location value by using a matrix-based approach to combine (i) the prior location estimate, (ii) said set of transition values, and (iii) said signal-based values; wherein said set of transition values includes at least one transition value representing the likelihood of the device moving between a pair of zones which are physically accessible from one another and at least one transition value representing the likelihood of the device moving between a pair of zones which are physically inaccessible from one another; and wherein said step of calculating a current location value includes using a discriminative model to calculate a current location value for at least one zone physically accessible from a zone corresponding to the prior location estimate, and a current location value for at least one zone physically inaccessible from said zone corresponding to the prior location estimate.