Photoshop needs a symmetry tool

Photoshop has yet to have a symmetry painting feature.  All the other programs I've tried so far still don't have what I'd like.
Corel Painter and Sketchbook Pro do have a mirror option, but they don't mirror the paint dabs!  They only mirror the paint strokes.
Krita comes pretty close, but it still doesn't mirror 'blender-type' brushes.

-Yet what I really want is a symmetry feature which mirrors both brush dabs and also fragments of photographs and other images I place into a canvas -kind of like a cross between a painting and a 'photobooth' application.

So I finally created a couple of actions in Photoshop to mirror one side of an image onto the other.  It can work with both paint and images.  The only drawback is it isn't instantaneous.  I have to activate the Photoshop action every time I want to mirror something.

The image above is something I did in a couple of hours just messing around with the actions I created.

Below is what I was cutting bits out of to make parts of the robot above.  Granted, I painted over almost everything, but you can still see some of it if you look close enough.