This chapter introduces commercial and emerging Radio frequency identification (RFID)-based applications in general and explores the suitability of the technology for a new purpose: wearable sensors and smart well-being-enhancing environments. It examines the possibilities of passive RFID technology in human body movement monitoring. The chapter focuses on passive ultra-high frequency (UHF) RFID systems, since passive tags are simple in structure, lightweight, inexpensive, easy to integrate into versatile objects, and offers virtually unlimited operational lifetime. It is possible to establish maintenance-free sensors, without onboard sensors or other electronics, by using passive UHF RFID tags as the sensing elements. The widespread use of RFID in other industries has resulted in attempts to introduce applications in the healthcare environment as well. RFID can also be applied in home environments. The tags may be used in the same way as the industry—in access controlling, tracking, and sensing. The medication industry is using RFID technology for anti-counterfeit and tracking purposes.