A good warm-up offers us about eight hours of "protection," and there is no substitute. None. Zilch.
That being said, apart from fluttering the lips and getting some good breathing going, the Heimat tone concept of Gerald Webster is extremely good for those (hopefully rare) situations where a "normal" warm-up is impossible.
Gerald Webster discovered that when we play a medium high, medium low, medium loud tone on our mouthpiece first thing in the day, the same pitch will come out, our personal "home" tone, or Heimat tone (he discovered this while touring with Edward Tarr in Germany, thus the German name). "Personal" means just that, each person has his/her own Heimat tone -- there is no "good" "bad" or "ideal."
Knowing our personal Heimat tone, we can start the quickie warm-up from there, expanding up and down, using mouthpiece or trumpet, and quickly focus in on our natural playing center. We can play with confidence because we know where "home" is.