Chris, I don't have experience in designing such systems, but here is one document that I think will help you in your design.
<a href="http://zone.ni.com/devzone/conceptd.nsf/webmain/D367783F087E57E386256CC90055172B";>Building Flexible, Cost-Effective ECU Test Systems</a> I was able to find few other articles when I searched on Google for "ignition switch" and labview. Zvezdana S.
