I was thinking about being able to give this phone commands without having to take it apart, connect the serial board, and a USB cable to the computer...
Things we could possibly do with commands is enable A2DP for high quality audio, or set volume level. I will have to finish reading this PDF, http://dlnmh9ip6v2uc.cloudfront.net/datasheets/Wireless/Bluetooth/rn-bt-audio-ug-2.0r.pdf, before I know the possible options I want to add.
The way I'm thinking of going about this is to have the user take off the hook, then push the hook in 2 times and this will bring it into setup mode. To choose an option, simply dial a number. I will have to make an option print out.
Example: To change the volume, double press the hook, then dial 2 for the volume option, dial the level you want, 1-9, 0 for cancel. When done configuring, just hang up the phone on the hook.
Now, with us adding in this option, it will be good to have some way to communicate with the user that settings take place or the settings mode is enabled. I am thinking of tones, so to do this... I would like to add an speaker into the phone to use the following tutorial http://arduino.cc/en/Tutorial/Tone.
We can use this for more than just settings, we can use this for a startup chime, a ringer if we end up not adding in bells, and other things.
Now the problem I'm having with this is deciding what resistor is needed for this Arduino as from what I understand the Arduino Pro Mini we're getting will output 3.3V the digital ports and the Arduino shown in the tutorial is probably a 5V Arduino... Arduino Pro Mini has a 5V version, but that requires getting a voltage regulator for the bluetooth board to bring it down to 3.3V... Leaving everything at 3.3V is the best option.
If I'm going to use this speaker as a ringer, I should probably just get an audio amplifier board and a big enough speaker to play a ringing tone.