Thanks dude!!!!
But, it is related to programming.
I want the hardware i.e. which ultrasonic sensor has to be used.
Or is there any other cost effective option available for same?
**broken link removed** MA80A1 can work up to 5 meters.
You need highly directional sensor to have as low as possible field of view. "Cost effective" depends on application mostly, so you have to define it yourself. These sensors are ~$150.-
There are a some application data available in linked document.