well ... nice to see that I am not alone in this trend of thoughts. Like most in this blog, I don't have the expensive equipment, but have been happy with my iphone and navionics app.
I just found out that apple also offers ($199) a dual GPS/Charger to be used with the iTouch (I believe it would work w/iphone too). This should take care of the "out of range" problem with signals - and the gadget also adds about 10 hours of GPS use, for those of us who haven't yet installed a charger on board ....
I also read some months ago a review on Sailing Magazine about several companies who offer a waterproof casing solution for iphones+itouch etc. Will be happy to track the magazine down if someone is interest, although I am sure googling it would do just fine.
What I would like to be able to do is to have a weather overlap with these apps, anybody have any experience/ideas?