I have an extra...
DEI Shock Sensor Model 504D.
This will add to the security of your car w/ OEM Alarm. I have posted a DIY already and its benefits have been discussed below.
I'm looking for $10 and the price of shipping, retail is ~$25. If you're in the Bay Area we can potentially work something out where I'll install it for you even.
Price: $10 + shipping from 94116
Payment type: Cash pickup or paypal only.
links for DIY and more material below:
DIY:
http://www.e90post.com/forums/showthread.php?t=45815
http://www.e90post.com/forums/showth...649#post674649
http://www.e90post.com/forums/showth...669#post599669
more references:
http://forum.e46fanatics.com/showthr...t=shock+sensor
http://forum.e46fanatics.com/showthr...t=shock+sensor
http://forum.e46fanatics.com/showthr...t=shock+sensor
http://forum.e46fanatics.com/showthr...t=shock+sensor