[icoder]

The IDFV already supports tracking user across apps, as long as they are from the same vendor. It resets when apps from a vendor are removed from a device. Not sure if the user can reset it by themselves, but the vendor could then always tie things together using another self-generated identifier stored on the device, as long as any of its apps are on it, which boils down to the same.

I think the approach you describe allows roughly the same, except perhaps doing so without (or with different) permissions, and allowing to do this between vendors (that must agree upon this upfront).

[e28eta]

I think it’s most interesting for 3rd party SDKs (analytics, advertising, others?), because they’re in a position to have their code running in apps from different vendors.