Hopefully increasing the response time to > 2s (whether it's settable in the API or just has a longer timeout) is on the roadmap, I can think of lots of future use cases where you would want a human in the loop on authorizations.
Looks like a great product and props to you and your team for shipping this.
That's not possible. Transactions need to be approved at the POS within a reasonable amount of time. Waiting for a human is to respond is not reasonable.
You could pre-approve the transaction and then confirm it within 2 sec though.
I can also imagine of lots of future, intensely frustrating use cases where a user scans their card in a line at a point-of-sale, or is waiting on a "Confirming purchase, please wait" page on a website while your human in the loop puts this approval on hold for a few minutes until your cell phone finally rings.
Currently, human-in-the-loop approvals do happen, but they happen long after the purchase goes through - ever gotten a call from your bank's card services department as you were leaving a gas station on a road trip? Much more convenient for the common use case where the human approves the transaction than the rare cases when the bank is on the hook for the stolen gas.
Since this is an API, that means you just build this into your app. You could initially decline the transaction, send a push alert to the user's app notifying them that the transaction is in review, then update them on that status when approved/declined. At that point the card can be run again and approved if that was the decision. You could even allow a pre-request through the app, when when approved would enable your user's card for the purchase. The possibilities are endless.
Looks like a great product and props to you and your team for shipping this.