A range/speed finder can be incorporated into a personal electronic device. In one example, a personal electronic device includes an automatic focus system adapted to focus an image of an object and a processor in communication with the automatic focus system adapted to detect a distance of the object using the automatic focus system. The processor can be adapted to detect a speed of the object and/or a dimension of the object using the automatic focus system. Methods and systems for determining a distance, a dimension, and/or a speed of the object relative to the personal electronic device are also provided.