GoogleMap map = getMap();
Navigator nav = new Navigator(map,start,end);
nav.findDirections(true, false);

nav.setOnPathSetListener(this);

Google Maps/Google Earth APIs Terms of Service

Last updated: May 27, 2009
...
10. License Restrictions. Except as expressly permitted under the Terms, or unless you
have received prior written authorization from Google (or, as applicable, from the
provider of particular Content), Google's licenses above are subject to your adherence
to all of the restrictions below. Except as explicitly permitted in Section 7 or the
Maps APIs Documentation, you must not (nor may you permit anyone else to):
...
10.9 use the Service or Content with any products, systems, or applications for or in
connection with:

(a) real time navigation or route guidance, including but not limited to turn-by-turn
route guidance that is synchronized to the position of a user's sensor-enabled device;

and may be disabled for certain apps (somehow, at least on Android)... FromGeocode
scraping in .NET conversation:
This is not allowed by the API terms of use. You should not scrape Google Maps to
generate geocodes. We will block services that do automated queries of our servers.

Bret Taylor
Product Manager, Google Maps

The Directions API has the following limits in place:

2,500 directions requests per day.
When the mode of transportation is driving, walking, or cycling, each directions search counts as a single request.
Searching for transit directions counts as 4 requests.
Individual requests for driving, walking, or cycling directions may contain up to 8 intermediate waypoints in the request. Waypoints can not be specified for transit requests.
Google Maps API for Business customers have higher limits:

100,000 directions requests per day.
23 waypoints allowed in each request. Waypoints are not available for transit directions.