You can get voltage (12v ignition from the voltage rail underneath the steering wheel)

BeenverlichtingInbouwen_NDPHOTO_20121014_005 by ND-Photo.nl, on Flickr
12v geschakeld = ignition

BeenverlichtingInbouwen_NDPHOTO_20121014_005 by ND-Photo.nl, on Flickr
12v geschakeld = ignition