Garmin, makers of many different GPS products, released details of their Mobile XT product. It comes in the form of microSD cards preloaded with maps and navigation software. With this you can use your phone like a regular garmin GPS receiver!

An additional online service is also available, allowing the user to get real time traffic & weather updates, and fuel prices.

"Garmin Mobile XT is easy-to-use and affordable, with no monthly
charges," said Charles Morse, Garmin's director of mobile and PND
marketing. "It's a one-time investment that gives customers full-featured
GPS navigation on their smartphone whenever and wherever they need it,
including areas outside of wireless network coverage."

The best thing is, the basic package is only $99!

More info here:
Garmin Mobile(TM) XT: Plug 'N Play Maps for Your Phone