1. A method comprising: augmenting a device by attaching removably a case thereto, the device containing a first set of less than six self-contained inertial sensors; providing a second set of less than six self-contained inertial sensors housed in the case, outputs of the second set of inertial sensors being coupled to the device externally through a connection, wherein there are at least six of the self-contained inertial sensors in the first set and the second set in total; providing, in response to correlated outputs from the first and second sets of the self-contained inertial sensors, an augmented time series including sufficient information to track changes in both position and orientation of the device being manipulated by a user in a three-dimensional space.