I've been investigating options for using a chart plotter on my boat. It looks like a good way to do it would be with the Navionics app and charts on my iPad. I don't have cellular on my iPad so I'm looking at the Bad Elf GPS Bluetooth device. Does anyone have experience with this setup? I already have a Garmin 550C fishfinder. I also have a Garmin 76CS GPS hand held that I use for getting from one waypoint to another, but I don't really want to add charts with such a small screen. I know there is some pretty high tech and expensive equipment available, but is it really necessary just to track where I am on the charts?