Tldr:

Hardware in the homebase,

Brainwaves on the walkways.

How to quickly destroy information etched into titanium disks or thick, marine grade steelplates in case of capture? Also carry a hammer when on the run or traveling through an airport/customs with your physical seed backup? They take the hammer out of my hand before they search the luggage.

A signing device offers slightly better protection but is far from perfect. Once customs got the idea that your device holds keys, they may try to force you to open it. Depending on the country and the circumstances - bitcoin being insanely valuable - torture can't be ruled out. Metal detector can also sense the NFC chip implant in my buttcheeks, that's no good.

Multisig is sort of a solution, brain key + steel key but I'm not on my own, my family should be able to access the funds if I don't make it and vice versa. A family of three traveling, two brain keys, one seed key? The physical device indicates that we own bitcoin, it also deems multisig useless as keys can be extracted from us easily.

No multisig and no physical copy of the key seems to be the safest way to move bitcoin through dangerous territory 🤷‍♂️