Great idea Ryan! I was looking at my own old WXTex 50 liter Pneumo Mech inflatable sack last summer and trying to see how I could make it into both a waterproof pack and inflatable mat at the same time. The problem with it was that I couldn't get the top closure to stay sealed when I lay down on the sack. I guess the only way to make it work as a mat would be to forego the pack idea and do what you did and seal the top. Another problem was that the sack bulged so much in the middle that it was impossible to lie comfortably on top of it for long.
For a pillow I recently purchased a Cascade Designs Lite Seat (a tiny version of the Therm-A-Rest Pro mat) that I inflate, fold in half, and retain with a rubber band. It's flat so my head doesn't roll off. It's insulated. I can also roll the seat into a rounded, toffee-roll shape. Plus I can use the pillow as its intended seat, as an extended addition to my BMW Torsolite pad, as an insertion in my G4 pack back panel, as a eyeglass or compact camera protector, as a Russian-style handwarmer, as a poor man's temporary "helmet" under my hood, as a foot warmer at the end of my sleeping bag, as a (though not great) camera "bean bag", as part of a splint for broken limbs, as a waterproof pack lid, or even as a chest protector against wild, boxing hermits!
Wow, just writing this gave me a new idea... an ultralight inflatable camera bag for my heavy Nikon D70s...
You're inspiring Ryan.