There're probably so many valid uses for it that I can't really come out with anything right now (apart of, obviously, keeping an eye on what's going at home while we're somewhere on holidays and receiving some notifications when something is moving in the flat while it obviously shouldn't), but hey, it's an incredibly cool gadget after all!
This specific model is a 3rd generation of Y-Cam's cameras and is finally 100% compatible with Macs, is able to transmit sound using industry-standard G.726. Furthermore, after a bit of hacking (on the client side) this cam's stream can even be viewed on the iPhone! (however, without the sound and in rubbish quality, but it's still better than nothing).
Of course, I told Natalie that this is our New Year gift (as obviously it's a bit too late for Christmas) but she somehow didn't sound convinced. However, she didn't sound annoyed too — after all, it's a useful gadget, unlike the great many we already have in our household :-)
Anyway, here's a link to this particular model: http://www.y-cam.com/y-cam-knight-sd#Specification. This is a nice promo video — also worth viewing. And finally, an all-excited review from one of my most trusted review websites (ironically, it's somehow found the way to it's name) — although it's a pre-previous model, it still gives some idea about what it is.
A downside is — I will probably get the order only after New Year. Yeah, it's bad, I know, but it's better than nothing and this idea just happened to me this morning. So let's wait and see, and I promise a full detailed review with photographs and videos as soon as I get this cam into my hands.