If interested in adding any of these new cards to Google Now, you can find the full list of working apps here. These apps are specifically designed to be predictive, basically attempt to supply users with information at the right time. For instance, the OpenTable app could display information about the cost of the check when a restaurant meal comes to a close. Through the card interface, you can launch directly into payment and leave the restaurant after paying for the check using your smartphone.
Other examples of these types of notifications could be reminders when your ZipCar reservation is about to end, alerts from RunKeeper reminding you to exercise to burn off the calories from your heavy lunch or perhaps Spotify offering playlist suggestions based off your recent music listening history. Of course, all the apps have to specifically be authorized by the smartphone owner and permission has to be given in order to appear in the Google Now interface.
At this time, Google Now integration is still being tested privately with a select group of third-party developers. Google is expected to open up the Google Now interface to all developers, but hasn’t announced a date in which that access will be granted. For the time being, it appears that Google will continue rolling out third-party support on Google Now with select batches of apps.