It sounds to me like what you are looking for is a standard electronic article surveillance (EAS) system, in which you put a tag on items and the system woul beep whenever someone walked through a portal holding one of those items. Such systems are available from ADT, Checkpoint Systems and others.
RFID potentially could serve the same purpose, and the technology could tell you which pair of slippers or which robe left the premises. If that is what you require, then you can use RFID laundry tags. These are available from a number of companies, such as Securitag Assembly Group (SAG) and Tagsys RFID.
High-frequency (HF) laundry tags have a fairly short read range (within three feet). If the doorway is fairly wide, you might need to use an ultrahigh-frequency (UHF) laundry tag. A single interrogator will likely cost approximately $1,000 to $1,500. The biggest cost with an RFID system will probably involve having someone install it and set up the software for you.
—Mark Roberti, Editor, RFID Journal
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