Feautures
The Car Kracker is a microcontroller with a bit of hardware to talk to your car. It plugs into a connector in the trunk and has several default modes built-in;
Audio Jukebox Mode: Play music stored on an SD card
Advanced Diagnostics Mode: Remove the Nav warning screen, access error logs and read / modify ECU characteristics
Bus Sniffer: Display data traffic and send test packets
Audio Aux-In Mode: Enable Aux input to stereo headunits
A kit is available, or you can follow the schematic in the next step to make one from scratch. Everything is open source, so it be customized and the firmware can be updated via USB. A few ideas;
Traffic Camera Alerter
Automatic Audio sync
Auto Unlock: Unlock the doors when a specific Bluetooth device comes within range
Data logger + phone home: Automatically send car location and speed via SMS
Will it work with my car?
The Car Kracker works with the following cars;
BMW
3-Series, 1998 - 2007 (e46)
5-Series, 1995 - 2004 (e39)
7-Series, 1994 - 2001 (e38)
X3, 2004 - 2010 (e83)
X5, 1999 - 2006 (e53)
Z4, 2002 - 2008 (e85, e86)
Mini
One / Cooper / S, 2001 - 2006 (r50, r53)
Convertible, 2005-2008 (r52)
Land Rover
Range Rover, 1999 - 2003 (L30)
Will it break my car?
Unless you want to update the firmware on your Engine / Transmission, It's pretty much impossible - the data bus is designed so that errant / malfunctioning devices don't break anything. Changing preferences (like turning off the door gong) just updates the settings memory, the firmware doesn't change.
Credits
The Car Kracker builds on many people's work - Many thanks to Dr_Acula for respinning RS232, Jochen @ Navcoder, the BMWCoders forums, Rayman for audio playback, e46fanatics, and bimmerforums. Thanks Everybody!
Continue on and I'll show you how to make your own!