I'm a Genius

I had a brainwave this morning while I was dropping my husband off at work at UVU today.  Wouldn't it be fantastic if cars came with some sort of device to indicate if a driver was planning to make a turn?  Maybe the driver could flip a switch and a little arrow would flip out to show which way they wanted to go.  Or better yet, they could install a little blinking light so you can see it at night, too.  I'll make a fotune on this idea while increasing public safety! It's brilliant!  Wait...