My sweetie and I both installed Navionics
on our iThings to use as backups for cruises this past summer (Lake Michigan & the Pacific NW). It was about $40 - the most I've ever spent on an app. I found it extremely intuitive, easy to use, and very accurate. It also has access to tide data and can create/measure routes. It only took me a few minutes to download charts
over a wi-fi connection. I downloaded another set almost as quickly over a 3G network. It's also easy to set display units (E.g. depth and speed).
While this might seem obvious, a key feature is its ability to download and store maps on your handheld
device. The significance is that once you download the charts
, you have the map data even if you're not in cellphone range. (Many of the places we visit have no cell coverage.)
But it's just an app- and while it doesn't provide things like AIS, it's still a pretty amazing tool.