A new update for Google Maps was released today and brings some impressive new functionality. Artem put it well (although perhaps not exactly eloquently): "it's #$%^ing amazing... Google keeps blowing minds." In a nutshell, Transit Navigation (as it's officially dubbed) brings exactly what you'd expect - it helps you navigate public transport. In their words:
Transit Navigation (Beta)
Google Maps Navigation (Beta) currently provides over 12 billion miles of GPS-guided driving and walking directions per year. Now, GPS turn-by-turn (or in this case, stop-by-stop) navigation is available for public transit directions in 400+ cities around the globe with Transit Navigation.
Transit Navigation uses GPS to determine your current location along your route and alerts you when it’s time to get off or make a transfer.