Ping))) sensor:
http://www.parallax.com/tabid/768/productid/92/default.aspx
Very accurate down to the Centimeter up to 3.3 meters. ~$30
Ping))) sensor:
http://www.parallax.com/tabid/768/productid/92/default.aspx
Very accurate down to the Centimeter up to 3.3 meters. ~$30