Nowadays, with the  mounting number of vehicles problem evolves how to supervise and keep an eye on driving  behavior of the populace. Many systems are proposed but none is proficient and uncomplicated to put into operation in real life. So there is necessitate for development of cost efficient and real time arrangement that can be implemented almost with every car. Exercising Smartphone is escalating as fast as forest fires. Features accomplished with Smart phones can be exploited in better way in enlargement and development of new systems. OBD(On-Board diagnostics) device in association with the Smartphone application can be collected into one system to diagnose driving behavior. OBD device gives real time information About Engine Control unit. Alongside with driving behavior we can get information about fuel consumption rate etc. We have projected a client-server real time car monitoring system which can be used by car renting companies to manage their rented cars and a knowledge-based framework for a driving assistance via Smartphone