The Smart Proximity Detector I have developed uses a PICAXE-08M to control the blinking of two IREDs. The detector mounted in the middle of the PCB determines if there is a reflection from the IREDs. Since the PICAXE controls when and how fast each IRED blinks, it knows what condition created the reflection. The detector is most sensitive to 38 kHz IR and gradually gets less sensitive as the frequency gets off center. This gives the PICAXE a way to "estimate" a distance to the reflecting object and if it is located across the robot, or just on one side or the other. Not only can an object be detected across the robot, but if there is significant difference in the distance on the left and right side, that can also be determined.
The boards tested fine, so look for kits on Nearsys.com/catalog shortly.