Under a new California law effective January 1, 2009. it is now illegal write, send, or read a "text-based communication" while driving. While most media outlets only make reference to the common practice of sending and receiving text messages from a cell phone, the new law also applies to any type of electronic communications such as testing, instant messaging and email.
First time violators will be fined $20 and then $50 for each violation after that. The law does not apply to situations where the driver is using a phone to look up a number to place a phone call. The law does not apply to "emergency service professionals" such as police officers when the electronic communications occur in the scope of their duties and while in an authorized emergency vehicle.
California drivers were previously banned from using their cell phones while driving unless they used a headset or a speaker. Passed in 2006, that law did not cover texting or emails.