A couple of years ago in the UK, there was a wing levelling/autopilot device
that used optical technology.
Basically, by sensing the difference in light level between the ground and
sky on the horizon the device was able to keep the plane in level flight and
on a straight heading.

It had an adjustable gain control that allowed the pilot to set the amount
of correction the autopilot applied.

I flew someone else's plane with one of these devices fitted and it was
pretty impressive.

I'm not sure if it would be exactly what is required here, in that it is
more of a stabilising device rather than a true controlling device.

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