Last week we launched an entirely rebuilt Directions component in Google Mobile Maps, adding Transit & Walking directions to the app - one of the top feature requests since the launch earlier this year:
If you own a Palm Pre, you'll automatically pick up the change in the Google Maps app. On the iPhone, you can bookmark a direct invocation path to Transit (http://maps.google.com/maps/m?mode=transit), which our Japanese users will see as a mobile One Google link.
Official post on Google Japan blog
(... and the English translation for those who can't read Japanese)