Initiate voice recording via Bluetooth dialling in car

I drive a car with a built-in hands-free interface to a Bluetooth phone (it's a Volkswagen Passat). From the "on-board computer" interface in the dashboard, I can select an entry from my contact list and dial that number to talk to them. I often find that, as I am driving along, I have a thought that I would like to remember by recording a voice memo to myself. The only way I know of doing this is to unlock my Android phone, start a voice recording application and hit the record button. By the time I've typed my pin number into my Android phone to unlock it, this is already very unsafe while I'm driving along, so I don't want to do this! Is there anyway I can set up my phone such that if I dial some "special" number (#\*#\*# or whatever) that, when I call it will just record my voice rather than actually dialling an external number? I could then program this number in to my contacts list and access it via the buttons on the steering wheel of my car. Ideally, when I hang up the call I'd like it to email me the recording, but that may be going too far... This would also be useful on the motorbike where the phone is in my pocket, but I can dial numbers (when safe to do so) via the Garmin Zumo 660 GPS. If I stop at some traffic lights, I can quickly dial a number on the GPS, but I certainly wouldn't have time to take my gloves off, unzip my jacket, take my phone out and run a voice recording application!