Looks like you soon won’t be able to do that at all.
University of Utah engineers have invented a wireless car key device to stop motorists from talking on their cell phone or sending text messages while driving.
Each driver of a car would have a separate key device. When the key is extended from the device, it sends a signal to the teenage driver’s phone, putting the phone in "driving mode" so it cannot be used to talk or send texts. The phone displays a stop sign while in driving mode.
The University has licensed the Key2SafeDriving technology to a private company, which hopes to have the device on the market within six months, possibly through cell phone plan providers.