WonderGel
I was able to get this on an airplane with little trouble.  It was definitely better than your average airplane seat.  After an hour, hour and a half or so, my a** still started hurting though.  I think that the gel 'columns' that they use are able to collapse too easily, would be nice if they were more firm.  I also agree with other reviewers that it could be an inch or two wider.  I can't really review it lower then 3-4 stars though, I don't know exactly why my rump hurts so much when I sit, can't really blame this product for that!  The true test for me will be when I take it in the kayak in a few weeks.  That's the real reason I bought it.
Rating: 4 stars