In environmental monitoring, such as air quality monitoring, accurate and continuous data collection through a wireless sensor network is of significance. In this paper, we describe a deployed and participatory sensing system which monitors the environmental parameters through deployed sensor nodes or crowd-owned sensors, e.g., smartphones with affordable additional sensors. The noisy sensory information is processed using a Kalman filter and an information quality metric is computed and used in an incentive scheme. In this demonstration, we show that the proposed system effectively monitors the environmental parameters with improved accuracy and coverage.