If I'm not mistaken, I dont think BMW offers a retrofit alarm option anymore either. I think only the Feb or Mar 09 MY are retrofittable...Not sure but I remember reading that here somewhere. (I had a retrofit alarm for my 09 in Feb, PITA and prob. more expensive)
If thats the case, make sure you decide now on the alarm.
09 E90 M3 DCT SSII Carbon Blk, Eisenmann Sport, RAC 19"RG63 on 255/275 UltracS, Dark Sidemkrs/Reflectrs/Grills, BMC Filter, LUX H8 V3 LEDs, V1 H/W, Ultimate Pedals & 30% Tint