Idea: Have devices in emergency vehicles that can change red traffic lights to green... for the direction they are headed or the lane they are in.
Already exists, and gets used more often than not.
While the normal flashing lights do get noticed, in areas with a lot of traffic sometimes there is no way to clear a path for oncoming emergency vehicles.
Triggering the light to change in advance allows that traffic to get moving again so it can clear the way for the emergency vehicle.
Idea: Invent a cell-phone-signal-blocker for a sunvisor or dashboard. Maybe with a 10 yard radius.
This could save some lives, help prevent some road-rage and make people pull off the road to talk.
Been done. It plugs into the car, and interacts with a software feature in the phone to disable most of the phone's functionality. Currently it is being marketted towards parents of teen and young adult drivers, and includes features like speed and location monitoring so that not only does it disallow cellphone use while driving but it also makes sure that a young driver is driving safely.
Check this out. It even comes with an insurance discount. https://www.esurance.com/drive-safe
This doesn't actually jam the signals, it simply uses bluetooth to communicate with app on the phone to disable sections of the phone's functionality.
Pretty much if you can think of it, someone has already made a product of it. And if not, you shouldn't talk about it online. Instead you should quietly develop and market a product and make a fortune from it.