Fish Finder for My Car
Whenever you see a TV report on floodings there's always some footage of cars that tried to make it down a road where the water turned out to be deeper than they thought, leaving them stranded. This device would prevent that. It would consist of 2 parts, one you hooked on to your front bumper and one that you left in your glove compartment until you needed it. When the need arose you'd pull the remote out of the glover and push a button. This would drop a rod down from the bumper device to the ground (it would have a small wheel on the end of it so it could roll). Once you reached the water the depth finder would look several feet ahead and compare the depth it found to the clearance under your car. If you couldn't make it a warning would flash on the remote. You could also turn the depth finder side to side to see if there was any way to make it down the road.
This device might be a little pricey but it would offer some major peace of mind to drivers like myself who run into roads like this a couple of times a year.
Reward: None required.