Smart Cities aim to improve living conditions by enabling new intelligent services for citizens. These services typically require environmental awareness obtained from distributed sensing systems. The implementation of such sensing systems on a city-wide scale is challenging, as the number of sensors needed can become unpractical. In this paper, we evaluate the utilization of mobile sensors as a possible approach to cover wider areas with fewer sensors and to use opportunistic communication to solve connectivity issues. In this direction, we propose a mobile sensor network using the public transportation system. To validate the feasibility of our proposal, we start by evaluating the performance of important commercial sensors in a mobile scenario, comparing measurements of static and mobile sensors of temperature, humidity, barometric pressure and luminosity. Our findings suggest that there is no or neglectful speed dependency on the measurements taken.