Manufacture or FORDS of the Motor home would give details of the type of alarm or immobiliser or both that are fitted to insurance standard. Or Fords will as they supply the moving part.
Over the counter purchased alarms appear not approved alarms unless stated 'insurance approved' but some insurers insist on profesional fits not DIY fits.
Check with insurers whats acceptable. You may get what the contributer thinks helpfull but insurer won't pay out if the unit goes.
Bob
August 2012