Similar systems are available attached to golf carts in nicer courses. I don't know about weather info or food availability, but distance to pin and elevation info is available. These systems will also keep track of your score. The disadvantage that current systems have is that many of them use an in-house triangulation system. In other words, they don't use GPS, which makes their systems more expensive and more difficult to maintain. The problem with GPS is accuracy, and the fact that the government can change the accuracy of the GPS system at their discretion. I don't know how accurate current GPS receivers are, but I would think that a golfer would want a unit that was accurate within 3 to 5 yards.
Would this be a unit that a golfer would purchase, or that a course would provide? I'm guessing that a course would provide the unit. Another thing to consider is size and weight. If I'm carrying my clubs, I don't want to figure out where to put a big, heavy device. A small form factor and low weight are key. Also, you may want to think of providing a clip system that would attach to a persons bag.
Ryan