It's already live, I had to go through it last week. It's in developer options, then it asks if you're moving the selector to allow the installation of non-play store apps because you're being asked to by someone.
Then it starts a 24 hour timer. When that hits zero, you have 1 hour to go back in and select that you want to install apps on a device you own and paid money to own.
It's not scam-resistant at all. Any scammer will gladly work around this and send someone to one of many malicious apps in the play store, or a malicious URL, or even just set an appointment to call Grandma back the next day.
Then it starts a 24 hour timer. When that hits zero, you have 1 hour to go back in and select that you want to install apps on a device you own and paid money to own.
It's not scam-resistant at all. Any scammer will gladly work around this and send someone to one of many malicious apps in the play store, or a malicious URL, or even just set an appointment to call Grandma back the next day.