It is for entertainment application, which gives car key sound as real car key.
Alarm Car Key is a very nice prank application with you, make your friend think that you can unlock your car with your phone.
Put your finger on button and you will hear the alarm sound continuously and led will change from green to red given an impression that car key is working and emitting radio waves.
The application also has enhanced features like vibration, screen shake and a flash light. You can turn off these features.
Note that is application is for entertainment purpose only and not working as real car key.