Hi Zombie,
You can read a little more about pressure mapping systems in post #2 here and post #4 here.
I would be very cautious because these are often used as a sales and marketing tool to sell specific mattresses that are made by a specific company and the mattresses that it “points to” are often lower quality/value that either use lower quality materials or don’t disclose the quality of the of the materials in the comfort layers of the mattress (which are the weak link of most mattresses).
The first place I would start your research is the mattress shopping tutorial here which has all the basic information, steps, and guidelines that can help you choose the best possible mattress … and know how and why to avoid the worst ones. You are most likely dealing with a store that I would tend to avoid in the first place (see the guidelines here).
If you let me know your city or zip code I’d be happy to let you know of any of the better options or possibilities I’m aware of in your area.
Phoenix