I created this project to make an open source solution to the social distancing problem. It only contains four items and is totally portable. The 9V battery can be easily replaced as needed and with a clear user interface no one will misunderstand what the lights mean.
The way the code is currently set-up there are three modes. Closer than six feet to the sensor is a red light, six to eight feet is a yellow light, eight feet and beyond is a green light. It is also lightweight and unobtrusive so it can be taken anywhere.
Nice that it's in wearable form, could be good for conferences. If we're ever allowed to go to them again, that is :-(