I have the Navionics App (
http://www.navionics.com/en ) paid like $50.00 to load all of the maps. It's pretty cool, has navigation channels, buoy markers, known hazards, depths, etc. But...because it uses GPS locator...it drains cell phone battery pretty quick. I left it running on a halibut trip back in June, on the way in, when we saw a pod of grey whales, I didn't have any battery to capture pictures. :sad: I keep a 12 volt charger on board my boat.