Is it possible to attach an object to the end of a curve and have the object point in the same direction as the end of the curve? I've come up with a few ways to do it but they're all hacks, and none of them work with the build modifier. 

I want something that will keep the object at the end even when the build modifier is being used so that the object seems to move along with the curve.

I was wanting to make something that looks like this: 





That way the cube is pointing along the curve no matter how the curve shape is modified. This seems like something that blender should be able to do on it's own.
You can do it with a little trick.




Create the cube and the curve
Create a plane at the exact same position as the cube and scale it down so it is inside the cube. Do it in edit mode so that its object scale won't change
Parent the cube to the plane
Mark the plane as dupliface in the instancing section
Add a curve modifier to the plane


This is the start of the curve, though...

Edit: to do it at the end of the curve


Parent the cube to the curve
Set the curve as 'path animation' with only 1 frame
Adjust the cube orientation so that it fits the first control point of the curve