Does your project require a simple rangefinder with a large range of measured distances? Why not try the HC-SR04 ultrasonic range finder?
This rangefinder can serve as an excellent sensor for a robot, which it can then use to determine distances to objects, go around obstacles, or build a room map. It can also be used as a sensor for an alarm that is triggered by the approach of objects or people.
The ultrasonic range finder determines the distance to objects in the same way as dolphins or bats do, echolocation. It generates sound pulses at 40 kHz and listens to the echo. The timing difference in the propagation of the sound wave can unambiguously determine the distance to the object.
Unlike infrared proximity sensors, the readings of the ultrasonic range finder are not affected by sunlight or color - even a transparent surface won't be an issue for this sensor. However it may have trouble determining the distance to fluffy or very thin objects. Therefore, it may be best to pick up many different kinds of sensors to have the most accurate results.
This rangefinder does not have a large choice of interfaces and modes of operation. On the flip side, this sensor is much easier to use and won't cause as much confusion if you're looking for a simple rangefinder. If you plan to use it with an Arduino you can use these existing libraries: