I'm new to the world of making, so I want to make the "detection of human" as simple as possible.
The easiest thing I can imagine is two materials which simply are in contact to each other when weight is on the object and move apart if not. This could simply be done by two connective materials I guess.
Hi! If you want to post a diagram in a hurry just draw it by hand and scan it in. Worked for me :-)