You can align the pivot along a selected normal which can be defined by vertices, edges or a face.

alignPivotToSelection.mel.c

//---------------------------------------------------------------------------------
// Source: https://www.highend3d.com/maya/script/align-pivot-to-selection-mel-for-maya
// alignPivotToSelection Tool for Maya 2010, 2011 & 2012
// Author: Daniel Brkovic
// Thanks to: Tom Ferstl
// Date: 10-12-2011
//
// Description: 
//		You can align the pivot along a selected normal which can be defined by vertices, edges or a face.
// Commands: 
//		alignPivotToSelection(0),alignPivotToSelection(1)
// Installation: 
// 		1. 	Copy alignPivotToSelection.mel to C:\Users\[USER]\Documents\maya\[MAYAVERSION]\prefs\scripts\jm991
// 		2. 	Restart maya
// Instructions: 
// 		1. 	Select at least 3 vertices(best), 2 edges or 1 face. 
// 		2. 	Run alignPivotToSelection(0) to affect rotations only and alignPivotToSelection(1) for rotation and translation.
// 			Note: Best results with 3 vertices, triangle or quad face selected.

global proc alignPivotToSelection( int $option )
{
	if ($option == 0)
	{
		ConvertSelectionToVertices;
		string $vtxSel[] = `ls -sl -fl`;
		string $selectedObjectStore[] = `ls -sl -o`;
		$objectSelectionStore = `listRelatives -p $selectedObjectStore[0]`;

		if (size($vtxSel) < 3)
			error "Please select at least 3 Vertices, 2 Edges or 1 Face";

		// create and align helperPlane
		string $plane[] = `polyPlane -w 1 -h 1 -sx 1 -sy 1 -ax 0 1 0 -cuv 2 -ch 1 -n rotationPlane`;

		select ( $plane[0] + ".vtx[0:2]") $vtxSel[0] $vtxSel[1] $vtxSel[2];
		snap3PointsTo3Points(0);
	
		// parent object to helperPlane
		parent $objectSelectionStore $plane[0];

		// freeze transformations on object    
		makeIdentity -apply true -t 0 -r 1 -s 0 -n 0 $objectSelectionStore;
    
		// unparent object
		parent -world $objectSelectionStore;

		// cleanup
		delete $plane;
	}
    
	else if ($option == 1)
	{
		setToolTo Move;
		float $getPivotPos[] = `manipMoveContext -q -p Move`;  
		ConvertSelectionToVertices;
		string $vtxSel[] = `ls -sl -fl`;
		string $selectedObjectStore[] = `ls -sl -o`;
		$objectSelectionStore = `listRelatives -p $selectedObjectStore[0]`;

		if (size($vtxSel) < 3)
			error "Please select at least 3 Vertices, 2 Edges or 1 Face";

		// create and align helperPlane
		string $plane[] = `polyPlane -w 1 -h 1 -sx 1 -sy 1 -ax 0 1 0 -cuv 2 -ch 1 -n rotationPlane`;

		select ( $plane[0] + ".vtx[0:2]") $vtxSel[0] $vtxSel[1] $vtxSel[2];
		snap3PointsTo3Points(0);

		// parent object to helperPlane
		parent $objectSelectionStore $plane[0];

		// freeze transformations on object
		makeIdentity -apply true -t 0 -r 1 -s 0 -n 0 $objectSelectionStore;

		// move pivot
		xform -ws -piv $getPivotPos[0] $getPivotPos[1] $getPivotPos[2];

		// unparent object
		parent -world $objectSelectionStore;

		// cleanup
		delete $plane;
	}
}

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

This was a great help for what I was trying to achieve; create locators and align them to faces.
Thanks for the upload!

Here is my script in Python, if you are curious:

`
import maya.mel as mel

def alignPivotToSelection(sl=None, translate=True):
    if not sl:
        print("Nothing selected")
        return
        
    face_pos = cmds.xform(sl, q=1, translation=True, worldSpace=True)
    # Find the average of all our x,y,z points. That's our center
    get_pivot_pos = ([sum(face_pos[0::3]) / len(face_pos[0::3]), sum(face_pos[1::3]) / len(face_pos[1::3]), sum(face_pos[2::3]) / len(face_pos[2::3])])
     
    sl_vertices = cmds.ls(cmds.polyListComponentConversion(sl, toVertex=True), flatten=True)    
    if len(sl_vertices) < 3:
        print("Please select at least 3 Vertices, 2 Edges or 1 Face")
        return
        
    #sl_object = cmds.listRelatives(cmds.ls(sl=1, objectsOnly=True)[0], parent=True)[0]
    
    # Create and align helper plane
    plane = cmds.polyPlane(name="rotationPlane", width=1, height=1, subdivisionsX=1, subdivisionsY=1, axis=[0, 1, 0], createUVs=2, constructionHistory=True)[0]
    
    cmds.select("%s.vtx[0:2]" % plane, sl_vertices[0:3])
    mel.eval("snap3PointsTo3Points(0);")  ### TODO Transpose this
    
    # Create Locator
    new_loc = cmds.spaceLocator()
    cmds.xform(new_loc, rotation=cmds.xform(plane, q=True, rotation=True, worldSpace=True), worldSpace=True)    
    
    if translate:
        # Move pivot
        cmds.xform(new_loc, translation=get_pivot_pos, worldSpace=True)
        
    cmds.delete(plane)


#sl = cmds.ls(sl=1)[0]
#alignPivotToSelection(sl=sl, translate=True)

sl = cmds.ls(sl=1)[0]
sl_faces = cmds.ls("%s.f[:]" % sl, flatten=True)

for i in sl_faces:
    alignPivotToSelection(sl=i, translate=True)
`