Arduino 101* includes on-board Bluetooth® LE to enable developers to interact with Bluetooth®-enabled devices such as phones and tablets.

The $22 kit includes an Arduino-BLE board and 6-pin header that should be fairly broadly applicable for building Arduino-based hardware that can communicate with iOS devices.

The hardware you would need could include, for example, a Bluetooth Smart Shield for an Arduino board together with a USB cable. The SSK is part of a wider Bluetooth Developer Program, which includes ...

The watch is built around an Arduino Pro Mini, a scavenged Nokia LCD, and a BlueSMiRF Gold. The Bluetooth connects to a Nokia N900 with a little Bluetooth client app [Ahmet] wrote.