The rising demand for ultra low power devices is the result of the desperate urge of man to conserve energy while continuing to enjoy the benefits of modern technology. Consistent and efficient sourcing of these devices is a test. RF energy harvesting systems are emerging as an efficient solution to this exigent situation since it harvests the otherwise wasted ambient energy. This paper presents an overview of such systems with reference to their design configurations, possible sources, applications and the current scenario in India.