shootRay

    ''' this Command fires a ray down the +Z axis of a locator at a mesh 
            and selects any poly that the ray intersects
            does not yet handle animated positions
        Command format:
            shootRay LocatorName MeshName '''

NAME_CMD_SHOOTRAY = "shootRay"
NAME_ARG_LOCATOR = "StrLocatorName"
NAME_ARG_MESH = "StrMeshName"

getScene  = lxu.select.SceneSelection().current
getSelectionService = lx.service.Selection
meshType = lx.service.Scene().ItemTypeLookup(lx.symbol.sITYPE_MESH)
locType = lx.service.Scene().ItemTypeLookup(lx.symbol.sITYPE_LOCATOR)

class CmdShootRay (lxu.command.BasicCommand):
    def __init__(self):
        lxu.command.BasicCommand.__init__(self)
        # Define the parameters needed by the command
        self.dyna_Add (NAME_ARG_LOCATOR, '&item')
        self.dyna_Add (NAME_ARG_MESH   , '&item')
    def cmd_Flags (self):
        return lx.symbol.fCMD_MODEL | lx.symbol.fCMD_UNDO
    def cmd_Enable (self,msg):
        return True
    def cmd_Interact (self):
        pass
    def basic_Execute (self, msg, flags):
        # Get the parameters needed by the command
        locIdent = self.dyna_String (0, "")
        meshIdent = self.dyna_String (1, "")
        try:
            if locIdent and meshIdent:
                scene = getScene()
                selectionService = getSelectionService()
                locItem = scene.ItemLookupIdent (locIdent)
                meshItem = scene.ItemLookupIdent (meshIdent)
                
                if (locItem.Type() == locType and meshItem.Type() == meshType):
                    posXYZ  = None
                    rotXYZ = None

                    # get the Locator Position
                    locItem.ReadEvaluated()
                    # get the Locator Position
                    channelValue = locItem.ChannelValue(lx.symbol.sICHAN_XFRMCORE_WPOSMATRIX)
                    positionMatrix = lxu.object.Matrix(channelValue)
                    posXYZ = positionMatrix.Get4()[3][:3]

                    # get the Locator Rotation
                    channelValue = locItem.ChannelValue(lx.symbol.sICHAN_XFRMCORE_WROTMATRIX)
                    rotationMatrix = lxu.object.Matrix(channelValue)
                    rotXYZ = rotationMatrix.Get4()[2][:3]
                
                    # Convert meshItem to a meshObject.
                    channels = scene.Channels(lx.symbol.s_ACTIONLAYER_EDIT, lx.service.Selection().GetTime())
                    meshChannel = channels.ValueObj(meshItem, meshItem.ChannelLookup(lx.symbol.sICHAN_MESH_MESH))
                    meshObject = lx.object.Mesh(meshChannel)
                    # get the polyAccessor (in order to get the polyId later)
                    polygonAccessor = meshObject.PolygonAccessor ()
                    
                    try:
                        # TRY TO FIND INTERSECTION - This code shoots the ray in the +Z axis
                        intersect = polygonAccessor.IntersectRay(posXYZ, rotXYZ)
                    except:
                        lx.out("NO HIT!")
                        pass
                    else:
                        # A HIT! and poly "selected" by the accessor
                        lx.out(intersect)
                        # get the polyID
                        polyID = polygonAccessor.ID()
                        # select the poly in the Viewport
                        polyType = selectionService.Allocate(lx.symbol.sSELTYP_POLYGON)
                        polySelectionType = selectionService.LookupType (lx.symbol.sSELTYP_POLYGON)
                        vertexPacketTranslation = lx.object.VertexPacketTranslation (polyType)
                        packet = vertexPacketTranslation.Packet (polyID, 0, meshObject)
                        selectionService.Select (polySelectionType, packet)
                else:
                    lx.out("Syntax should be: shootRay locatorName meshName")
            else:
                    lx.out("Syntax should be: shootRay locatorName meshName")
        except:
            lx.out(traceback.format_exc())

#         shootRay Locator Sphere
lx.bless (CmdShootRay, NAME_CMD_SHOOTRAY)        

Thanks to Farfarer, Matt, Captain Obvious