What a wonderful idea.
First you want to put devices in cars that often produce erroneous results, and require that people driving cars use them continuously in order to drive. (I wonder how distracting it will be to respond to the warning that you have to blow now before the car stops while driving down a crowded freeway.) Then you want to make it impossible for people who are within 100 feet of a car with the engine running to be able to use their cell phone, even if they want to report a drunken driver. Keep making me safe like this and and you will kill off everyone in the country.
You guys are like, well, retarded. My blue tooth device doesn't find my cell phone if it is right outside my car...and my remote key doesn't work if it isn't right in front of the sensor.
Ya'll live is some past world of non-remote controlled televisions and transister radios.
And you just proved how little you know about electronics.
Your Bluetooth device does not find you cell phone outside your car because if has a limited transmission range. In order to disable cell phones inside the care you would need a signal powerful enough to override the cell phone itself, which can has a range a bit further than your Bluetooth. There is no way to make that work only inside the car. In fact, the least powerful cell phone device available blocks phones for about a block. I was deliberately low balling my estimate.
As for your key, I suggest you change the battery. That should be able to work from at least 25 feet.