Actually, it is a 2 hour tour that takes you on the back trails at Fort Wilderness.
Here is a
link to more info (it's at the bottom of the list).
It's not all that expensive- it's $85/person, but there are discounts available for AP, DVC and Disney Visa. (I think it's about 15% off)
You do have to be 16 or older (no kids allowed) and able to stand for 2 hours.
I am in decent shape, but my knees got very tired standing still in one position for so long!
The info page lists it for 3 days/week, but in a recent phone call to ask about the tours, they are now doing this tour almost every day of the week. It is very popular!
I have not done this Segway Tour yet (planning it for Jan 09), but we have done the Epcot tour twice and loved it both times. I think the backwoods version would be very enjoyable as well.