The Calendar could use a GPS to decide how much lead time an alarm notification requires.
E.g. if you are going to a meeting in the same building, a 5 minute alarm is sufficient; ditto a phone meeting; but if you have to drive 20 miles, you probably want half an hour or more notice.
Most existing PIMs that I am familiar with make the alarm lead time a property of the Meeting or Appointment item. Really, the alarm lead time is a property that the Calendar should calculate, based on geographic position and nearby Calendar items.
(Part of
AndyGlewWishlist20030130)