Yumiko Tanaka is a graduate student at the Royal College of Art in London. There, as part of a project to explore the way adults and children play and interact together, she developed the Plable.
It's a concept for a table with an upside down play surface on the underside, which kids can build and manipulate from within "their own" little space while parents use the top side of the table. The playscape can change and react to parents moving things around above, too. Depending on how engaged you are in the play, this can either be seen as "interacting" or "dad messing everything up by moving his coffee."
Tanaka came up with the idea after remembering an incident from her own childhood where she'd put stickers all over the house, which her annoyed dad would remove after she'd gone to bed. When she realized he'd missed the stickers under the table, she explained, she "started to think of that as my secret space. Since then, I put many stickers on the underside and tried to create my world."
See more info and a demo video of the Plable at Tanaka's website [yumikotanaka.net via wmmna]