Organisations that have financed cars on the basis of a residual value that now seems unlikely to be realised will be trying all sorts of things at the end of finance contract to try to recoup some of their losses. I don't know about Telematic 'killer switches', but that is certainly feasible. The car could be rendered immobile at a location that the Telematics relay to the finance house if the debtor fails to make payments. I think what will become increasingly common is faults being found with the car on its return and the customer being hit with excessive rectification costs.