It is not a stupid question at all. if it can be done I am sure several people will be interested. You are correct that it can be done on the iPhone (e.g. http://www.inavx.com/
). iPhone developers have a significant advantage - they only have one screen/size user interface to design for, and other well defined hardware (gps, memory size, processor speed etc), and a large 'install base'.
I think this http://mapnav.spb.ru/site/page.php?15#navi
will do some of what you want - but I don't believe it will display nautical charts (in the UK at least).
would do what you want but you'll need to source/scan the charts yourself and upload them etc. I know someone who used it with OS maps for one trip (on land) but decided it was such a PITA to get the data in it wasn't worth doing. If you were always using in the same place then it might be OK.