A cool system would be a tool to find the location of a point relative to the sun. So I can whip out my smartphone while in the asteroid belt and have an intuitive metric system to identify any point in our solar system.
You'd need at least two more points of reference, I think, in order for this to be effective. By itself, a picture of the sun (and I'm assuming it's an incredibly clear picture taken with a magical instrument) would only tell you how far away from the sun you were.
With an additional known point (and an accurate date and time), you'd know where you were within a circle around the line between those two points. That might actually be good enough for a rough estimate, if you can assume that you're in the plane of the solar system.
