Sharp IR sensors are used to measure the range to distant objects at ranges up to 150cm. These work great on robots for obstacle detection and navigation both indoors and outdoors. These sensors come in a variety of range capabilities so be sure to check our store (http://stores.ebay.com/UPGRADE-INDUSTRIES) if this doesn't meet your exact requirements. They work quite well with Arduino, Raspberry Pi and BoardX. Check below for specifications as well as tips for designing your circuit.