The vibrator in a cell phone is made up of a very small motor with an offset weight on its drives shaft. When the device is switched on the rotational movement of the object weight causes cause resonance. When the motor spins; this weight causes vibrations through the handset due to its offset position. if the weight would have not been at offset position then there would be no vibration. you can control by the options given in the mobile to switch on the vibrator or off it. so, this way mobile vibrator does work. it creates good excitation in us.