Stanley Intelli Tools Ultrasonic Distance Estimator
is no longer available although you may find similar or newer versions below:
The Stanley Intellimeasure 77-018 Ultrasonic Distance Estimator measures distances up to 12m/40ft at ±0.5% accuracy with an easy to read LCD screen.
It calculates area, estimates materials for flooring, painting, wallpapering etc
Requires a 9V battery (not included).