Gowalla is a a location-based social networking game that runs on Apple iPhone, Google Android, Palm WebOS and RIM BlackBerry devices. Gowalla users can visit certain locations or follow routes in their vicinity, and receive or exchange "items", which are generally small icons or "mission pins."
Gowalla also occasionally offers the ability for users to win real prizes, and the Eye-Fi promotion is a particularly generous example. Gowalla users will need to visit their local Apple Store or Best Buy location, and "check in" using the application. 500 random users will receive an instant notice that they've won a free Eye-Fi card, while the remainder will receive a coupon code good for one year of free hotspot access upon purchasing an Eye-Fi card.
More details can be found on the Eye-Fi blog.