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I've been playing with openCPN at work for a project here at work for the last few months. If you don't know what it is, openCPN is a freeware char plotter and gps navigation software. You can download the source code and hack it to your hearts content or run it as built. For those of you with eyes on a larger boat this may be an option or for those of you who don't want to drop a couple of grand of a chart plotter and gps.
I'm sure someone out there has figured out a hack to put this on a smartphone vs using your laptop.