Well, the ActionMap stuff could be moved into a different folder of helper utilities.. But, as they are very app specific, never part of OIS core.
As for being convaluted, I don't see how.. The class just overrides all the listener events, searches a Map for the trigger (button, axes, etc etc), and calls the callback function. Pretty simple and straight forward. One thing that it could use though, is more template binding (perhaps through the use of Fast Delegates).. as, now it only binds class member method instances. It does not yet to static binding.. but not to difficult to add. And, it is really just an example right now.
For instance, in WGE, I use a Map with the trigger id, and a String.. The string is used to call a Squirrel Script Function callback... And, I combined the ActionMapping stuff directly into the same class that initialises OIS, as the code is very small.