This is the kit I have installed on my X,haha not exactly $2 bucks,but yet less expensive than an OE retrofit.
Anyway,to OP,in the control box,when you unscrew it,you'll find 4 adjusters with screws,one for each sensor,just play with it,so it gets a bit less sensitive to the pavement.I was able to find the point of almost no useless beeping.

http://www.ebay.ca/itm/REVERSING-PAR...item51967b7c09

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e53 '00 4.4i Oxford Green II Freshly rebuilt tranny(2nd one) and transfer case/front shaft
e70 '08 3.0si Sapphire Black cinnamon leather 7 seats
e61 '06 530XI Sports Touring Silver - SOLD