Radio Frequency Identification (RFID) technology has recently being favorably considered as a cost-effective alternative for indoor location tracking. However, most current implementations use active tags and conventional middleware, which are more expensive, complicate to use, and may not work with other pervasive devices such as IP Multimedia systems or cell phones. In this paper, we propose an RFID-enabled location tracking system, SIP-RLTS, based on Session Initiation Protocol (SIP). Our proposed solution can be used for both Push and Pull location tracking modes and can be used with either active or passive tags. The use of SIP infrastructure, coupled with the proposed location-oriented middleware extension, Ontology infrastructure and semantic integration, making SIP-RLTS a more cost-effective solution for the next generation communication services.