the easiest way to make one object follow another is to create parent-child relation between them.
There are two methods to create such relation.
First method is attaching. It creates a relation and adjust child’s position. This method is described here, but it is not applicable for camera object since camera doesn’t have any slot for attaching.
Second way is to make one object child of another without changing anyone’s position. Unfortunately at the moment it is possible only by executing build mode script. You should write simple script like this:
After executing this code axe becomes child of camera:
Now by playing script axe always follows camera