Just picked up a used 2012 135i DCT a few months ago, this is the first mod I've done...and it's close to paying for itself already!
-Beltronics STI-R Plus (includes GPS): one of the best units, includes GPS (a must IMO). Remote install is great...I've had a few friends with their windshield mount detectors stolen (window smashed & loosing a $500 detector is terrible!). This unit has laser jammers as an option (whereas the equivalent Escort unit automatically includes the jammers and costs more for it), which is the main reason I went with Beltronics...b/c I wanted a better laser jammer.
-Blinder H-905 Triple: supposed to be top of the line...and so far it's worked great. only downside is that the speaker is in the main unit and it's not very loud...I'll re-locate it closer to the driver's seat.
Installed on the lower center console: this piece is fairly easy to remove, it comes out w/ the A/C control unit. I mounted the speaker behind this area...I may drill a few holes to allow more of the sound out (at higher speeds w/ windows down it's still audible, but not as alerting as I'd like)
night shot: easy to read, out of the way.
Front radar receiver: had to cut some of the honeycomb grille, routed wire behind bumper and through passenger side, and then down through the wiring box). used good double sided tape on the whole surface of the unit...no issues holding.
wiring/units: used velcro to attached them on the upper surface of the passenger footwell...it's out of the way and easy to access.
Blinder front units in upper grilles: had to cut some of the grille material. could have mounted them further recessed, but jammers work better when they've got a clear view. Most laser jammers cover a side-to-side range; in order to cover the headlights/license plate (main targets) I had to mount them horizontally.
Blinder rear unit: mounted just below the license plate. body is painted with BMW Alpine White, matches fairly well. only portion that's not white is the face of the unit which sends/receives.
Side shot of rear unit:
