I believe there would be a good market for a simple daylight viewable
flash memory chartplotter capable of displaying NOAA charts.

Define good market. How many units?

It's one thing to see relatively cheap devices being made for the consumer
market. But that doesn't directly translate to a device suitable for the
marine market. The durability demands of the marine market would make it
considerably more expensive. That and the number of likely unit sales would
also keep the price high. Cranking up a production run of a million units
allows greater efficiencies and reduces costs. If you're only building a
few thousand at a time your costs are much higher. Then there's the
marketing, sales and support costs.

As for using cell phones, no thanks. Having suffered through thunderstorms
and other rough seas I'd MUCH rather have a weatherproof setup built-into
the helm. A handheld would end up going overboard, or at the very least
getting smashed by dropping on the deck.

Sure, it'd be a great idea but it seems there's just not a large enough
market to do it at a low price.