Mike sent in this link to a video (short) about the use of NFC and parking payment and access control. Yep, before too long (2-4 years or less they tell me) all phones will be NFC enabled. When they are, you phone becomes a credential just like you AMEX or Visa. You simply wave it near (within an inch or so, hence Near Field) the sensor and VOILA, you have been identified and have paid for you parking, called an elevator, opened a door, or soon to be in many places, paid for your coffee or Big Mac.
This technology brings further ease of usage to the parker, and makes it easier to use pay by cell in many applications. There are security issues, but they are being addressed as the technology becomes more pervasive and is also used as a mobile purse, enabling you to carry money with you without the need for coin or bills.