Valentine sells an attachment that let's you plug into the OBD port. This makes "hard" wiring easier, and it also includes a speed sensitive function so you can trigger the alerts to only come on at a certain minimum speed.
I have this and am very satisfied.
2012 BMW E93 M3 | Mineral White | 6MT
2013 BMW X5 xDrive35i Sport | Black Sapphire
2015 BMW F10 M5 | MCB | ZCP| MPE (On Order)