BackJoy seat support
The Posture+ by BackJoy Orthotics (Greensboro, GA; 800/222-5569) is a portable sitting device designed to prevent pressure points from developing by tilting your pelvis upright and distributing your weight evenly. I tried the product over several weeks while working and did have a more upright posture when sitting and a decrease of pressure on my tailbone.
I think it could be beneficial on long flights, though its size (15.3"x13") and rigid design make it cumbersome to take along. (It is only 0.5 inches thick but has a fixed curve, making it 4.4 inches in depth.) It weighs 14.24 ounces.
The Posture+ ($39.99 plus $7.95 shipping in US) is available in six colors and works best for people weighing 120 to 300 pounds. Sizes for those weighing less are available. — Beth Habian, ITN