it gives out a set of frequency, which is very near to our max precieve-able range.
the higher the frequency noticeable-able by you, the more active you are.(note:not for person to person fatigue comparison.)
you set the frequency to min and increase until you can't see the led flash (it will appear as if it is constantly on)
Note: you'll have to look directly at the led, with it being right in the centre, since out corner of eyes can sense higher frequency.
You'll need extremely dim led for the project
Step 1: My Version
It is in a bit of narcissistic art with my initials engraved into the putty that I used to shape it.
The opaque side is made with epoxy and a section tic-tac candy box.
the led is the dimmest types of green LEDs I have in my collection
I've used a 470K variable instead of 250K to accompany higher reaction time suitable for gamer like me (the prototype with 250k wasn't reaching high enough frequency in-noticeable by my eye.
(for hyperactive kids, a higher resistor might be needed)