I think having a radiant heating system under a slab foundation would be a wonderful idea. Our basement floor is always so cold that you never want to go down there without socks or slippers on.
Something like this sounds like it might be pretty expensive to install, and it would be much more cost efficient if you had it put in before you poured the slab.
I have a friend who has radiant heat like this in her bathroom which has a tile floor. When you walk on this floor when it is cold outside, it feels so warm and cozy under your feet. I know we would spend a lot more time in our basement if we had something like this to keep the floors from being so cold.