This distance measuring assistant will greet you, measure distances to objects continuously and read the values out loud. It can be programmed to activate alarms when the measured distance crosses a user-programmed limit.
Got a pair of U/S distance sensors and an RPi ready? Then go.
Rather than designing a dedicated PCB, Elektor Labs used their ELPB-NG (that's Elektor Labs Prototyping Board New Generation) for the project. It's available from the Elektor Store.