My Garmin eTrex Legend has fishing and lunar tables. It can tell you when the sun will set, when the moon looks like a cookie and even draws you the position of the sun and moon. You can even make that play and watch the moon move. What really amuses me are the fishing and hunting things. It would be great if the GPS somehow knew that fishing is impossible if you are not near sea/river/lake. Exactly the same is with hunting. It’s kind of hard to do that in the middle of a huge town.
So I would like a GPS receiver that knows where it is and recognizes things around itself and uses that data for providing better info for the user. Too hard?

[...] This person has the right idea. He has a GPS and wonders why it can’t tell him where it is, “It would be great if the GPS somehow knew that fishing is impossible if you are not near sea/river/lake. Exactly the same is with hunting. It’s kind of hard to do that in the middle of a huge town.” He has a point there. So why aren’t GPS more intelligent, after all, they do have maps onboard, which do have features. [...]
Yea, they probably could make a gps like that.
But you’d have to wait about 10-15 years while
they build the infrastructure to support your
desires. And even then, you probably couldn’t afford it.
I know that it would be pretty expensive, but oh so useful. We’ll have to wait to year 2022 or something to find out. Sounds like sci-fi. :)