I just saw some interesting photos that indicate to me at least that Pres. George Bush Sr. wears a Patek Philippe watch. Note the distinctive crest on the clasp:
story.news.yahoo.com/news?tmpl=story&u=/050219/ids_photos_wl/r448611038.jpg
There's another picture that shows the front of it. It's not very clear, but I wonder if it's a 3940:
story.news.yahoo.com/news?tmpl=story&u=/050220/ids_photos_wl/r2692296970.jpg
If so, it's rather interesting, as it seems it is quite unusual for U.S. presidents (and, I suppose, former presidents) to partake in non-American luxury items, such as Italian suits or Swiss watches.