Have you seen Navionics? I've used it a few times now and I'm impressed with the level of detail on the map. It shows depths, shoal buoys, and channel markers and of course speed. It even shows private docks on the map I'm currently using. It is also linked with Google Maps and shows streets so you can navigate to locations based on streets around the body of water. However, there doesn't appear to be a way to enter an address. You can also set up a route, mark waypoints, and have it track your movements.
