It is an Analog VM Meter.
Analog Voltage Unit Meter Pedal (Analog-VUMP) – Joyemusic.com
I use it when I build my patches on the HS Stomp to help get them equalized. It also helps me to know how much signal that I am sending to the main board. It is passive and doesn't do anything to the signal. They have three models. Two variants of the analog, one with only 1/4" and one with both 1/4" and XLR. They also have a digital version that is smaller.
The YouTube shows an older version with a level knob that adjusts the level of the meter. The newer version that I have just has a 3-way switch that is 0db, -10db, and -20db. I think mine has a calibration pot inside if I wanted to calibrate it to a known signal, but I really don't need that. I just want to compare different patches to make sure they are roughly equal. Calibrating patches to a meter doesn't tell the full story, even patches that seems to be the same volume can sound to my ears louder or quieter, but the VUMP gets me really close quickly.
And the pedal looks cool.