Wearing a hard plastic safety hat may protect you from falling debris. If you have to work on your own at some remote location, a rock or a rivet or a plank which lands on your head may well just render you unconscious.
Today’s invention is an alarm fitted inside all such hats which is activated by any impact large enough to cause concussion.
Any such impacts would be sufficiently strong to drive a prodder mechanism within the helmet far enough to reach a particular button on the user’s phone (stored in its crown). This would send a text message back to base.
It would then cause the phone to issue a few squawks, so that anyone within earshot would rush to help.
The effect would be to minimise injury caused by lying unattended for a while or perhaps staggering around whilst disorientated.