Distance beeper

Not sure the terms I need but looking to build two device one transmits that you put on something and the other that starts to beep/buzz when other pass the distance of 10 feet away. I would even be nice to have it so you can adjust the distance before it beeps. I know of stuff that beeps when you get to close but trying to make so beep when it gets too far away. I there something already on the market please let me know.

Thanks

You would obviously need a modified version of ultrasonic/laser distance meter circuit which can trigger a beeper when it reads the particular distance -that would obviously need a microcontroller brain. Happy to help you