Object[] objects =FindObjectsOfType(typeof(GameObject));foreach(GameObject go in objects){
        go.SendMessage("OnPauseGame",SendMessageOptions.DontRequireReceiver);}

And to resume call OnResumeGame on all objects.

A basic script with movement in the Update() could have something like this:

protected
 
bool paused;voidOnPauseGame(){
        paused =true;}voidOnResumeGame(){
        paused =false;}voidUpdate(){if(!paused){// do movement}}