I was just talking about something like this with my gf last week. I want a big bed with upturned edges (but still big enough to stretch out fully on the flat part) that I can fill with extra cushions and blankets. The image in my head was a bit nicer than a giant dog bed though...
I remember something like this with a friend's water bed. It was mostly a normal king size bed setup but the rim of the bed had a 3 or 4 inch wide padded lip. It all came out to level when the bed was made but the effect as you got on the bed was sinking down a little past the lip, so even if you were on the edge you were still sort of cupped into the mattress instead of being able to easily roll out.
Yes! I don't want my pillows falling off the sides, I don't want my phone to fall off the edge, I don't want my blanket slipping over the edge. Right now I create the little lip with a rolled up t shirt on the edge so I can put my phone down and roll over and in the morning it'll still be on my bed