In the back of later editions of John Muir's Idiot's Manual, there is a quick easy procedure for installing a warning light that warns older bus owners when they have left their engine compartment lid open.  Looks like less than $10 buck in parts from your local hardware store and a not much technical knowledge required, because let's face it, if you drive into your garage with the pop-top up, you may be lacking in the knowledge department ;^)

Peace, JB
'66 Split Window Camper
'83 H20 Vanagon

"You cannot simultaneously work for peace and prepare for war..."