This already works for external devices, this request is specific to the host device itself. We can make use of Android's Keystore system to generate and imports keys to TEE or more dedicated secure elements (e.g. Pixel's Titan Security Chip).
What would be great as well is providing a wrapping key to facilitate secure transfer.
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I have looked at this enough to give you a straight answer rather than a hopeful one. On Android, Keystore exposes signing and decryption for the algorithms it supports, but never the raw key material, and OpenPGP needs operations Keystore does not offer for the key types PGPony generates. Ed25519 support in Keystore is recent and partial, and the post-quantum composite material has no Keystore representation at all. On iOS the wall is higher still: the Secure Enclave only holds P-256 keys, which OpenPGP barely uses, so a full "master key in the secure element" is not buildable today on either platform.
What might be buildable is narrower: a hardware-backed subkey slot for classical algorithms, treated the way card-backed keys are treated now, where the hardware signs or decrypts and the app never sees the secret. Your wrapping-key point fits that shape too, since Keystore's secure import is exactly a wrapped transfer. I have logged it for the Android 4.3.0 and iOS 8.3.0 cycle as a feasibility spike first, commitment after, because I would rather tell you it is hard than promise it and quietly drop it.
NorseHorse
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