In some posts that I have found, people made their own ultrasonic beacons where the user carries the beacon and the robot detects the origin of the beacon signal and follows it.
Could you link me to some of those posts that you have found on ultrasonic beacons so I could better understand what it is?
replicate this with a cheaper setup?
Cheaper than what?
In the video, the robot sends a wireless message to the ultrasonic transmitter module (on the wearer), telling it to emit a ping. The wearer's module must have a microprocessor of some sort.
In the Ben Heck Show, they used a xbee module for the wireless communication. However, xbee modules are quite expensive, so I was wondering if a nrf24l01 or some other cheaper wireless module would be able to replace the use of the xbee module.