The ABS sensor is in a pretty vulnerable spot in my opinion.  BG used to make a guard for it, but he shut down his shop, so I decided to make my own version.

As I do with most of my fabrication projects, I started with a manila folder and a pair of scissors...

Once I got the template right, I started work on the prototype.  Made from 0.0625" aluminum, it is quite strong and should protect the sensor from rocks, sticks, falls, whatever.  But, the thickness did present an issue...

0.0625 inches is equivalent to approximately 1.59 millimeters.  Well, the BMW specification calls for the ABS sensor to be between 0.1mm and 1.0mm away from the slotted ring.  Obviously adding an additional 1.59mm is going to cause the sensor to be too far away from the slotted ring.  The picture below clarifies what I am talking about--I'm inserting a 1mm feeler gauge between the sensor and the ring...

After a lot of thinking, I came up with a solution. 

Using a hand file, I removed enough material from the "sensor-mounting plate" (see picture below) so that when I reinstalled the sensor with the guard in place, the distance was in spec.

Here's the final product...