The Navionics Mobile program on my iPhone resulted in greater than two hour back up times for the phone on the MAC. I didn't use it enough to appreciate additional features but went back to MacENC where I find chart downloading is quite fast and not required very often. On the dedicated chart plotter on my boat, the Navionics GPS is right on, but the cartography is sometimes in error for my cruising area of southwest Florida. I haven't compared the Navionics Mobile to the Navionics chart plotter chip, but found MacENC puts me in the right place when the plotter says I'm in the mangroves. John Farnham M/V "Salty Doll" Punta Gorda FL (Disclaimer: a generally satisfied MacENC/GPSNavX and Navionics user with no other connection to either company)