A soft mat with a bunch of led lights embedded in it.
When you lie on it, it squishes in the middle, and all of the lights on each side of you point inward to what you're working on.
It would be useful for working under sinks.
Maybe a version with tracks for a creeper for working under cars.
would be nice it could run on a drill battery. If it had a hole in the center, you could wear it as a light poncho for creeping around in attics.
I would also like a separate inflatable mat that would bring your lower back and legs up to bottom of cabinet + light mat level.