It has to suck to own a "smart" domain after the term has lost it's flame, so it's worth noting that the time to sell may be limited. For example, if you have a "smartphone" domain, you might want to consider dropping it if no one's biting, because people are starting to just call them "phones" now. If someone wanted to give me "smartphone.com" for free I wouldn't even bother. My point is that the "smart" wears off once a product becomes the norm....
When "smart clothes" become the norm (or if they ever do) people will just call them clothing and so on....