Here's a little something I've been working on for a bit. It's all concept at this point because i haven't had time to actually build the thing. I've been spending quite a bit of time with my car, trying to get some repairs done. At some point, I'm going to gut the underside of my center console and re-do all of the wiring for my stereo, CB, GPS, and RFID reader. If I have time this weekend, I'm going to build this thing though:
The way it works:
A voice changer from a toy (Optimus Prime helmet) is removed down to the board. The Mic is hooked up inside the project box with some holes to gather your voice. The board skews your voice into the sound of a robot. The wiring for the speaker is removed and instead goes to a bluetooth headset's mic wiring. The sound coming out of the board is then broadcasted through the phone to the caller. The reason i am doing it this way is to try to cut out as much of my actual voice as possible. There will be 2 wires going into the headset only, which shouldn't hinder your ability to wear it too much. I am planning on powering the box with the board by using a re-purposed cell phone battery. A call gets made, and your modified voice goes through the headset. The person on the other end's voice comes through the speaker on the headset.
Now, assuming i can make this work, I will be able to make hilarious calls to people without them knowing who i am. Hrmm... We shall see.