Re: ipad as instrumentation...
Using an iPad has a few challenges, and solving them doesn't leave it cheap:
1) not waterproof
2) waterproof cases that don't make the screen harder to read and which allow you to use a power cable are expensive
3) ones with good mounts for a sailboat are even more expensive
4) NMEA integration is very expensive
5) Our two iPads aren't the 3G models, and the Dual brand bluetooth GPS that we have for them doesn't have an internal compass, so the heading information is interpolated and almost useless.
By the time I solve all of these problems it seems cheaper and better to just get a Raymarine a67 (which is the new cheaper variation of the e7d). The smaller size is nice too, and I can use the iPad as a big display inside the cabin if and when I need to.