I agree with Charts and Tides. I didn't realize the wi-fi iPad doesn't have GPS so it's not as useful for me on the water. The Navionics app for droid is excellent, and a bargain at $10. There's also a droid app called "currents" which elegantly shows you a map of a body of water with arrows indicating the projected current strength and direction at any given time. (longer arrows = stronger current). I have not been able to find anything as simple as that for iPad. And it's free.
Loving my iPad as a home computer I keep on the coffee table, but will be leaving it there for sailing and using my droid phone for chart plotting and a backup for GPS on the boat.
Keep the expenses low and the good times high.
PA Freshwater / Chesapeake