The Devantech SRF10 is an ultrasonic rangefinder with a I2C interface that combines a self-contained design with minimal power draw. Able to measure in both centimeters and inches, the ranging module can measure from 3cm to 600cm (1.2 inches to 19 feet).

The SRF02 is a single transducer ultrasonic rangefinder in a small footprint PCB. This Devantech ultrasonic sonar ranging module has I2C and Serial interfaces with a range of 16 cm to 6 m (about 6 inches to 19 feet)