Patent ID: 7027820

Claim:
A static but movable device, comprising: a short-range wireless receiver; a location-data processing arrangement for deriving successive estimates of the current location of the device using location data received on an on-going basis by the shortrange receiver; a move detection arrangement for detecting indications that the device at least may have been moved, and a location-validity supervisor for determining, following detection of one or more indications by the move detection arrangement, whether the current location estimate is to be treated as still valid, the location-data processing arrangement being arranged, in response to the location-validity supervisor determining that the current location estimate is invalid, to discard that location estimate as current and thereafter use subsequently-received location data to derive a new current location estimate, wherein the move detection arrangement comprises both a first detector arrangement for detecting a first said indication in the form of an indication that the device has physically been subject to motion, and a second detector arrangement for detecting a second said indication constituted by a change in the set of nearby devices from which the subject device can receive transmissions via its short-range receiver; the location-validity supervisor being responsive to the detection of a said first indication to query the second detector arrangement as to whether said second indication is present, the location-validity supervisor determining the current location estimate to be invalid when both said first and second indications are present.