Just some notes for now. The goal is to control an Arduino from a mobile phone via Bluetooth. The base is an Arduino and a RN-42 based Bluetooth hardware (https://www.sparkfun.com/products/10393). Arduino test code from https://www.sparkfun.com/products/10393. This code relays data from one device to another. On the phone the app BlueTerm is used. In the app I use Menu/Connect Device, then selects the "RN-42...". The things I then write in Blueterm shows up in the Arduino IDE serial monitor. Nice!