USB-ProxSonar-EZ1 MB1414 Ultrasonic Distance Sensor

The MB1414 USB-ProxSonar-EZ1 sensor features one-inch resolution and serial data over an easy to use USB interface, providing both proximity and range information for the nearest detectable target.
The USB-ProxSonar-EZ line is designed to detect people or obstacles that enter within a calibrated detection zone. The USB-ProxSonar-EZ proximity sensors report when a person or other detectable target enters the detection zone. The target is released after leaving the USB-ProxSonar-EZ's detection zone.
The MB1414 has a detection zone of ~5 feet. The MB1414 will allow for 8+ simultaneous sensors depending on sensor mounting and environment.

For more details, see the datasheet here