but plenty for an Arduino Nano. So far functionality for three of the four buttons on this speaker has been preserved: power, volume up, and volume down. The fourth button initiates Bluetooth ...

Bluetooth LE is good enough for short-range ... A small, cheap board was needed that could be powered by a LiPo battery, and [Micah] created a board that fit his needs perfectly.

Arduino boards get a Bluetooth Smart dev kit from Nordic Semiconductor. The SDK is compatible with a range of Arduino, ChipKIT shields that employ the nRF8001 Bluetooth Smart connectivity device.