How can you tell if a helmet is on your head?

Question

Do it yourself

A soft button above the crown will not always work if you have lush hair.
Temperature sensor - too large spread t, i.e. again, fuzzy operation.
IR LED and photodiode between ears?
Are there any other options?

Answer 1

Chin closure that completes the chain

Answer 2

Soft button closer to the forehead, there is more pressure and less hair

Answer 3

Try to play with or with these IR sensors:
www.acroname.com/articles/sharp.html
Just pick yourself up with a minimum distance.
Or alternatively Pyroelectric sensors:
infraredsensorformobile.blogspot.ie/2013/03/pyroel...

Answer 4

distance sensor. It means something like this: xrobot.by/sensors/ir_reflective_sensor (Infrared reflection sensor)