The Little Bramper developed by Thomas Bethel has been designed to assist timelapse photographers in achieving flicker free time lapse video during transitions from day to night or night to day.
To achieve this the system precisely controls the timing of the bulb exposure when the camera is in bulb mode and can automatically ramp the exposure duration, up or down, to correct for the change in light at dusk and dawn.
More information on the Little Bramper can be found here
First timelapse attempt with the Little Bramper system using a Canon 7D and 10-22mm lens with the exposure being ramped from 50ms upto 3500ms including a iso step change from 100 to 200iso. Not perfect but the errors are down to me rather than the Little Bramper.