Ken Hite recently dreamed up what he calls "Bad Omens" mechanics for the Game Design Contest at Ropecon. He says, "The important thing about an omen is that it comes true. Otherwise, it's just a creepy piece of atmosphere. This means that bad omens are primarily useful only in games in which the social contract admits that the player-characters are screwed. (A bad omen in D&D, by contrast, is just a killer GM trap -- "Save versus divine fate, DC a million.")" He applied the concept to Unknown Armies with these results:
"For Unknown Armies, the player may buy off any BOHICA (critical fumble) by accepting a Bad Omen instead. Again, the GM should tailor the specific Omen seen (mocking voices from the traffic lights, a hearse with the PC's birthday as its license plate) to the circumstances and to the player character's foibles (and to his Avatar or Adept school, for choice). The GM then rolls an Omen Increment as above, except that the player only and always receives three BOHICAs at the derived crisis. (This is the Wiccan Rede in game form, it belatedly occurs to me.)"
To see more about Bad Omens and other ponderings, visit Ken's LiveJournal.