Sounds like you/porsche can allow lock/unlock access via blockchain, using smart contracts. Does this open the door (no pun intended) for governments to deliver subpoenas for getting access to locked cars? Convenience is always at the expense of freedom.
Do you think this could be used by rental agencies and car sharing services without having to be managed by Porsche? What about privacy; would it be possible to identify the current occupant of a particular car from inspecting a public ledger?