First - I believe it is not practical to take a Segway from Rome to Pisa, if for no other reason than I don't think the batteries last that long.

The Duomo is about 1.6 KM from the train station, and this link gives you directions. Google says it takes about 20 minutes, which sounds right:

http://maps.google.com/maps?f=d&sour...55661&t=h&z=15

That having been said, Pisa is worth little more than a quick look if you must see the tower - it leans. My friends in Firenze always told us to avoid Pisa, but we thought we were just seeing the old Firenze/Pisa rivalry. They kept finding reasons for us to not go along the lines of "a chance for a special lunch just came up today...." but we finally escaped and made the trip. They were right. On the other hand, we fell in love with Lucca.