Google is expanding its free Google Maps Navigation to more Android devices, including those running Android 1.6 (Donut) and higher, such as the T-Mobile myTouch 3G and the G1.

Google rolled out the free feature for Android 2.0 devices – like the Motorola Droid – a few weeks ago in what many considered a game-changing move. At the time, shares in navigation device makers Garmin and TomTom took a steep tumble.

In a blog post yesterday, Google said its latest release includes the new Layers feature, which lets users overlay geographical information on a map. Users can view My Maps, transit lines, Wikipedia articles and more.

Google Maps Navigation is an Internet-connected GPS system with voice guidance and automatic rerouting. Users also can use Google search, typed or spoken, to enter their destination and get fresh map, business and traffic data.

Google Maps Navigation is in beta. Some features of Android 2.0 are not available on Android 1.6, such as the ability to use the "navigate to" voice command.