99 percent, I'd say.
Anyway, if you search you may be able to find some application that runs outside of quakelive that will let you bind a key, countdown a preset amount of time, and then play a sound. No more "cheating" than using Teamspeak or Ventrilo, IMHO.
Or you could just buy a few chess timers and label them and actually press the buttons once you take an item. Unpreventable hack?
Unless of course the timer would only show if u saw the item being picked up or heard the sound of it and didnt otherwise count if u didnt do either.
what about this guy? he's just regular player and records his own videos, and some kind of script is showing powerup timers:
http://www.youtube.com/user/uberfriedguy