I've always been fascinated by "rock speakers", i.e. audio speakers hidden in faux-rocks. Quite a weird object category, very ironic actually. There are some available on Amazon (see this one) and it's quite intriguing to read the technical features as well as the reviews by buyers. I can see that as an example of Invisible technology, perhaps in a different way than Mark Weiser's definition of Ubiquitous Computing.

What does it mean? What's the need to hide technology in a crappy plastic stone?