As far as portable Bluetooth speakers go, Jawbone's Mini Jambox falls short of being our favorite; it's more expensive than the competition, without being significantly better. Given that, then, you might want to take this post with a grain of salt: The company just announced a new feature called Multiplay that allows you to turn the tiny Jambox into a stereo speaker. The catch? You need not one, but two of these $150 units to make it work (N.B.: They're priced at $130 right now, but only as a limited-time offer). Assuming you can pony up, or have a friend with the same speaker, you can send music from one to the other by holding down three buttons on the device. Or, you can play the same song through both at once, with the option to designate a right and left speaker, allowing for a wider soundstage. (The Mini already has a "LiveAudio" feature that does basically the same thing, except the effect is subtler.) Given the prohibitive cost, this is a fairly improbable setup for most folks. That said, if you happen to own the Mini, and have access to a second unit, you can enjoy the feature now through a free firmware update.
Jawbone Mini Jambox