Presumably you would have to have the Starling app always running in background at least to get location, and it would be a massive battery drain?
Am sure it will be optional, but I always try to avoid any apps that need to montior location continuously. I wish the telcos would hurry up and (with user permission) license personally identifiable cell site data to services such as this, your phone already checks in with local cell sites, why waste battery making superfluous GPS checks too.
Also bear in mind that the location attached to the transaction on the payment side of things may be miles away anyway due to being a) a remote transaction - i.e. Ecom or mail order, or occasionally b) wrong full stop due to a business owner re-using an old terminal and merchant account from another premises or business of theirs without notifying their bank or changing the details. Recipe for Starling support enquiries!
(I’ve written and managed payments fraud software in the past and what sounds good as an idea, can have any number of false flags, all of which create support overhead).