Find out which camera you are working with

getCurrentCamera.mel.c

//---------------------------------------------------------------------------------
// Source: https://acaciaecho.wordpress.com/2011/08/05/maya-get-current-camera/
// Author: Zhang Jian
// Date: 08-05-2011
//
// Description: 
//      Find out which camera you are working with. Focus on a model panel, 
//      in which you can have a camera to tumble/pan/zoom, and run getCurrentCamera, 
//      you will have the transform name of the camera. 
//      If you are in some other type of panel, say outliner, empty string will be returned.
// Installation: 
// 		1. 	Copy getCurrentCamera.mel to C:\Users\[USER]\Documents\maya\[MAYAVERSION]\prefs\scripts\jm991
// 		2. 	Restart maya

global proc string getCurrentCamera()
{
	string $camera;

	// First get the panel that currently has focus
	string $panel = `getPanel -wf`;

	// Compare the panel's type to confirm it is a "modelPanel"
	if ( "modelPanel" == `getPanel -to $panel` )
	{
		// Get the name of the camera using the ‘modelEditor’ command
		$camera = `modelEditor -q -camera $panel`;
	}
	
	if($camera == "")
		return "";
	
	if(`nodeType $camera` == "camera")
	{
		string $rels[] = `listRelatives -p $camera`;
		$camera = $rels[0];
	}
	
	return $camera;
}

Remove the ".c" from the filename when you download this (git doesn't support .mel syntax highlighting)