Two other companies make optical cutoff switches that may be what you're looking for. There is a review on RCU on the smart-fly optical cut off. The other is Electro Dynamics. I do not have one yet, but will be picking one up shortly. These are truly isolated from the ignition by the fiber optic system.

[link=http://www.smart-fly.com/Products/Ignition/ignition.htm]Smart-fly-[/link]
[link=http://www.electrodynam.com/cgi-local/SoftCart.exe/t107.htm?E+scstore]ElectroDynamics-[/link]