I've been using the Navionics app on my phone and used it all summer. It's only $10 or $15 for the full version (Navionics+ charts, as many areas as you want to download) on a phone, $49 for the iPad). It also contains the crowd-sourced bathymetric data that's accumulated from participating users' sounder data, so it's almost as good as having local knowledge (maybe better in some cases) and certainly better than government charts which are not surveyed frequently.

The auto-routing function works well. There is never a situation where I wouldn't check however, but it's been my quick "go-to" app when I want to do a quick estimate of how many miles a route would be (or when the admiral asks for an ETA to an alternate destination when contemplating a change in our plans).