PricePlunge offers the X-Mini KAI Bluetooth Speaker, model no. XAM11-B, for $15.99. Coupon code "coldplunge5" cuts it to $15.18. With $1.99 for shipping, that's the lowest total price we've seen for one unit and a current price low by $8. (We saw two for $30 shipped last fall.) It features a built-in mic, mute button, and up to four hours of Bluetooth playback time.