When you HIT your BRAKES and get any type of Vibration or Wobble.....This means your rotors are warped!
Death wobble as everyone knows it as is simply a wobble at all speeds and gets worse the faster you go. it's very noticeable in 4wd
If your rotors aren't the problem. Worn out tierods can cause steering wobble when brakes are applied as well, but generally people would experience "wander" while on the highway if the tierods are bad.