Why do you need "many people"? Would it not work if you just had one person, who in any given period would either stare at you or not stare at you, on the result of a coin flip?
How's this:
You sit in a chair. Another person sits or stands behind you. There is a light in front of you, which both of you can see.
When the light comes on, the person behind you flips a coin. If it comes up heads, he stares at you. If tails, he stares at something else. You write down whether you think he is staring at you or not. The person behind you writes down whether he actually stared at you.
Repeat many times. Start with ten and work up from there.
At the end of the test, compare notes.