If you have an unused speaker in the basement collecting dust put it back to good use with The Vamp (£35; roughly $55).
This diminutive cube-shaped box gives your aging gear new life by providing a Bluetooth link to your phone or tablet and a 4 Watt single-channel amplifier that can drive even large speakers with surprising gusto.
The whole thing is powered by a rechargeable battery that lasts for over ten hours, and can connect with speakers that boast on-board terminals or wire coming out the back. Shipping in June in white, red, or black.