The iPhone app demo gives you an idea of what to implement
Canpages is running a nation-wide API contest for developers who can build an app for iPhone, BlackBerry, Android and/or web. The Canpages API gives you access to over a million Canadian businesses, and they’re looking for an app with a great UI and a lot of features. The contest has started and there doesn’t seem to be any entries yet, so there is still plenty of opportunity to win. Canpages will reward one grand prize winner $5,000 in cash, as well as three runners-up with $1,000.