I was using parry in a non-impulsive sense;
I hear ya.
I'm curious how you redirect without contact; doesn't Newton's first law have something to say about that? Or do you mean misdirecting the blow before it is launched, feinting and slipping?
You can redirect a blow without contact by working with the opponents perception (reflexs and limits). Two basic ways come to mind at the moment. One always changes the vector of the attack when done and the other can change the vector or merely get the opponent to travel further along it than he wants.
To change the vector you can take advantage of a persons tendency to track a target. I think most of us have had the experieince of trying to slip a punch too early and experiencing the resultant pain from your partner walloping you because he tracked your movement (adjusted and followed you). Well you can use that to your advantage. You can move in such a way that you get your opponent to track you... but you remain out of range or slip it in another way toward the end of his intended strike. This will pull his fist of the original trajectory, often unbalancing him and leaving you intact.
If you move along the vector but out of range you get only the overextension, if you subtlely move off the vector you get a "true redirection".
This method is I think most easily applied playing with wrist grabs. Have the opponent try to grab your wrist fairly quickly and with a reasonable amount of force. When his hand is just about to close around your hand... move your wrist backa few centemeters. If he believes he can still get it easily, he'll extend his attempt. Once you get that down, you can move the wrist away in little half and quarter circles. When he adjust to grab it (he must think its within grasp), he'll technically change his vector. From there you can experiment with using it against other grabs and punches as well.
Likewise, and this is the one that's great for parties, you can substitute a false target. the basic party trick version of this works like this. Opponent punches at your face. you bring your hand in front of your face then out to the side (at the right moment). The opponent will normally see the hand, subconciously (there are also some ocular reflexs involved) substitute the hand as the target, then track the hand as you move it to the side.
Its pretty impressive when you first see it. It takes a while to get the timing down, but the guys I know who really have this well (Shidare Yanagi Ryu Aiki Ju Jutsu guys tend to be REALLY good at this) can make people miss almost everytime. Of course its good to have a back up defense in case it doesn't work. I wouldn't rely solely on it a real fight. However recognizing its existence, can let you ad that dimension into your movements so you can get a more pronounced reaction from your opponent even when using movement to avoid them.
Also keep in mind that is sort of the base version of the skill. Later you apply the kill to gettting the opponent to track the wrong parts of your body while you are in motion doing other things.
I'd add my vote to jellyman's suggestion, a sort of 'defanging the snake' - attack their weapons (or is this what you meant by stop hitting?).
Yeah, I pretty much see that as a version of a stop hit. Sometimes I'll move my head back and put my elbow where it was... then I see it as a combination of stop hit and get out of the way.
I don't know if it's a Systema habit, but I find it handy to strike at the bicep of a curving punch if I want to close to grappling range;
I do that sometimes. Its a cool move that really unerves the opponet

More often than not I use it for illustrating a point about opening up peoples mind about the nature of "ranges", since you can create a lock/grapple situation from pretty long range.
Hoping to start a school up here in Holland, but I'm getting back into regular training first.
Let us know when you want to start training people. We have a couple of Newbies over on the Systema board looking for some instruction in Holland. I'll tell them to come over when you feel its time.
This is turning into a pretty cool thread I think. Neat.
Arthur
PS thanks Jelly