Is there a way to add hardware into a phone that is separate from the phone itself but can still interact with it from the inside to sign transactions and truly keep your bitcoins in your phone?
It is, but it was discussed and it's a very bad idea (read below). Plus, it makes the phone unnecessarily more expensive for people not needing that feature, hence not good for business.
And if someone stole the phone, they still have to unlock it with possibly a passcode, Face ID, Touch ID, and any other walls of security such as passwords to open apps.
I’ll have plenty of time to restore a wallet real quick I guess while the monkey whole stole my phone tries to get inside it.
Unless that monkey also steals you (or a picture of you) or your finger, or the last items you've had your fingerprints on.
No. Phone security is
weak and "the monkey" may move your money out before you even notice the phone is missing.
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And about your initial question, I think hat Samsung had ideas in that direction, but a quick search has only revealed
this topic (2021) and
this one (2019) on the matter.
