Sony has been selling the iGo (formerly Think Outside) Stowaway Universal Bluetooth keyboard as the VGP-XTBTUE for $150 since at least the middle of last year. I got mine from eBay for less than $100, I think, but it turns out that had I waited a handful of extra months, I could’ve gotten it for free. Well, free with the purchase of a UX280P.
The VGN-UX280PK1, the newest UX addition at SonyStyle.com, is shipping now with the folding keyboard and an Express Upgrade to Windows Vista for $1,800. The bundle-less UX280P retails for the same price and both "versions" are available, so be careful when placing your order.
You can see a couple of pictures of the keyboard and the "detachable UX stand" (as Sony calls it) in my UX180P stand options review. The keyboard is excellent, but the stand doesn’t withstand a lot of detaching. Mine is a few "detaches" away from breaking.[Micro PC Talk]