In my argument I have stressed the use of Video Technology in goalscoring situations and within the box, and also to adjudge whether a ball crossed the line.
The intentions of a fouler or handball situation are a huge grey area. It will still be the referee's call whether it is ball to hand or otherwise and the same goes for fouls; some will be allowed and other will not - a foul a not like a offside or ball crossing the line.
Video refereeing will not always help with diving. But where it is clear that there is no contact then a ref cannot award a penalty.
Tripping over a defender's leg is a big grey area. First, at the speed some of the players approach the box or execute a turn or dribble it is always going to be hard to judge whether they deliberately tripped over a stray leg or not. A defender that sticks his leg out in the box is also asking for trouble - the defender obviously had put his leg their to disrupt the player e.g the Lucas Neil against the Italians.
We have seen situations where a player had tried to stay on his feet and/or try to dodge a stray leg or tackle; then not been rewarded because he lost the ball.
If there is absolutely no contact and there is no obstruction* then the referee will have to not give. Whether they punish the fallen attacker is another issue - I think a lot of armchair pundit incl ex-pros are quick to judge the modern players and accuse them of diving. As long as the player is not rolling around and badgering the ref for a foul or a card then they should not be punished.