Abstract: We are at the end of a four­year effort that has dramatically improved the capability of the use of RF sensors, particularly those that measure received signal strength (RSS) to sense the locations and context of people in buildings and homes.  We have investigated both systems which use RFID tags to identify a person or object, and those which use a static deployed network of transceivers for device­free localization, to locate people moving in the environment who do not carry any tag or device.  Locating people who don’t wear a de