intuitive motion specifier

I keep having an idea in slightly different forms about how it would be cool to be able to move elements in some GUI and then have the code for doing that appear automatically. I was first thinking about this in the context of having my young son learning to program. I tried Alice and Scratch and a few other kid friendly software kits, but surprisingly none of them had the ability for the user to move an element around, i.e. intuitively specify what it's behaviour should be, and then have that stored as a behaviour that could be repeated, reversed etc.

The same idea came to me again in the context of game design, e.g. in a game editor like GameMaker or Unity3D is would be great to be able to "show" the system what kind of motion you wanted, and have the corresponding behaviour appear in the editor in a form that could be manipulated. Of course it wouldn't work simply for all behaviours. Getting one object to follow another would be trickier.

The thing at the moment is that I can't see how to add such functionality to any of the existing systems that I have looked at without geting very deeply involved in them. I could build a demonstration interface in JavaScript, but by itself it wouldn't be able to do very much. I have the feeling that eventually this functionality will appear somewhere and some people will go "oh cool" and I will be kicking myself for having not done anything with the idea, or it is already present in some software somewhere that I just haven't found yet ...