There are devices that are designed to be used by the scoliosis patient to correct curvature when sleeping. The most common one is the Charleston Bending Brace. This device has been used with varying success rates and most scoliosis surgeons do not use it anymore.
A general device for spine posture would probably not be too effective as it, by nature would have to create pressure points on the body which would be uncomfortable to sleep with.
Dr. Corenman