The “Natural Wave” is a ceramic plate that sits on a steam radiator, making it easy to keep drinks and muffins warm. And only muffins! It’s not rated for bagels or toast by the National Ornamental Snack and Hotcakes Administration (NOSHA).
It’s also not real, or at least not available for purchase. It’s just a concept by Byung-seok You, but something similar should be easy enough to cook up for yourself should you live in an old building that still has radiators. (Unlike my building which has modern heat that is never actually on.)
Radiators Have Other Uses Too [YankoDesign.com]