Re: Would love to see the look...
There is nothing that says if your car is unlocked by someone after you have locked it you can't claim.
Wouldn't matter, there's a range of established precedents in UK law that require the policy holder to exercise due care, absent which their claim can be dismissed, regardless of what the detail of the policy covers or does not. And likewise the policy holder must declare all potentially salient facts and risk factors, even if the insurer doesn't ask specifically. Not to mention things like the Insurance Act 2015 and other relevant legislation, plus insurers' "General conditions" documents, and the probability that signing up to a service that enables remote unlocking would potentially qualify as a "modification" to the vehicle.
Because of those two duties of care and disclosure, if you plan to either remotely unlock your car for a third party, or allow them to unlock it themselves, then unless you have told your insurer that you plan to do this AND they have agreed to cover all potential risks, then you will not be covered for theft of vehicle, contents, damage to either, or injury or loss to third parties.