Does a Disclock count as cat two ?
....some insist upon it, which is not good if you have spent all weekend installing one yourself to find the insurance company wants an installation certifcate.
This gives you the current list of after market Cat2 immobilisers which are Thatcham rated (which again your insurance may insist upon). http://www.thatcham.org/security/pdfs/categories/PassengerCarCAT2.pdf
Wow that list of new apporved systems is small.
Re certification - well if you happen to have a car where the system was 'already installed' you can always have your system inspected & certified by a local VSIB installer for ~£20. Keeps insurers happy.
Sorry you cannot do this now as the VSIB went bust last year