Can you elaborate more ?? Do you mean a simulation tool or something

I mean a real time sensor data generator  that generates data without physical sensors not wireless sensor network (WSN) simulator. 

ohhh ok. I am not sure if I can help but You can try googling V-REP or Webots.

These are simulation tools where you can add a sensor and get its reading. Of course, you will have to simulate the environment you want to test in it