We plan to eventually release an Android version of OpenTripPlanner Mobile. We're prioritizing the iPhone client because there's a more pressing need with iOS 6. Native mobile applications take time to build, however, depending on the success of this campaign we may be able to accelerate our schedule for an Android version.
We'd love to see global coverage and hope to offer that at a future time. However, the U.S. and Canada have been far more successful in opening up transit data. In many other countries data is not available or is shared only with Google. We hope that this project will highlight the downsides to restricting access to this data and encourage sharing.
There is a new API for transit. However, that API just helps you find apps that provide transit info for your area. If you're planning a trip from within the new Apple Maps app it will help launch the transit app of your choice to plan a trip.
Here's a great overview of what's known about transit services on iOS 6: