The Little Bramper (oh the classic original, no longer in production)

Little Bramper: Bulb ramping time-lapse intervalometer
A standard intervalometer simply fires the camera shutter according to a set interval. The Little Bramper added an additional configuration and not only fires the cameras shutter but also varies the cameras exposure smoothly over time.  By subtly varying the exposure, time-lapse footage of light varying scenes can be achieved.  For example a brighter sunset (faster shutter speed and low ISO) might fade into a night scene (slower shutter speed and higher ISO).

google Little Bramper website to learn more.

Comes with 2 extended cables and carrying case.  Used a couple of times, see pictures