The VCNL3020 is a integrated proximity sensor that works via infrared. Interface to the sensor is with i2c and it can measure up to 200mm in distance. The only back draw to the sensor is the lack of ability to change the i2c device address which can be a problem. Currently the schematic above only works with 3.3V systems.
It is meant to be used in cellphones to detect if the phone is against the users head. This makes the single locked i2c device address make sense as you would not just more then one of these sensors on a phone. With 16bit precision and a build in IR emitter its a pretty powerful proximity sensor even with its i2c address limitation.
Files (Eagle V6)
Bill of Materials
Part: Value: Package: C1 0.1uF 0402 C2 0.1uF 0402 C3 22uF 1206_POLARIZED C4 10uF 1206_POLARIZED R1 4.7K 0402 R2 4.7K 0402 R3 10K 0402 R4 10 0402 U1 VCNL3020-GS08