One phone call?

Once upon a time it used to be (well, if you believed the television shows) that people who were arrested and taken off to jail would be allowed one phone call. Today, I was listening to the radio and the report came in of a teenager who was tweeting on her way to the police station - and this tweet had been picked up by the news media. Does this mean the one-call limit no longer applies - if it ever did - especially if you have a smart phone or another way of connecting to the Internet?