Even better than a Tempurpedic, because they last longer, is a latex foam mattress. They are expensive, but are much better. As they say about Memory Foam - it loses its memory after a couple of years.
We needed a new mattress and did much research and checking. The solid block latex foam lasts longer and relieves pressure better than anything else. Yes, they are pricey, but they are well worth it.
Some stores put a layer of latex in, and then all kinds of other things. You want the SOLID latex - where it is done as a solid block, not stacked pieces and layers.
If you are in the SE Wisconsin Area, Milwaukee Mattress has a store downtown right off the Plankinton exit off I-43 NB (before the Marquette Interchange) They also sell them at Ken Michaels Furniture.
You can buy another brand, but if you'd like to see how they are constructed, you can go to http://www.kenmichaelsfurniture.com/
Go to the mattresses tab and click on the latex rubber and the pressure relief links and read about them.
The name brand mattress companies are starting to make these, too, so you should be able to find them in a Sealy, Serta, etc.