This looks interesting!
The new update to nostr-signing-device has support for multiple nsecs and a bunch of other cool stuff
PR https://github.com/lnbits/nostr-signing-device/pull/19 by nostr:npub1794vv7hl7y6q2qw0y7m7h60rpphmvt5h7pzt5sr78z6assj6w0eqagwjhd

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Discussion
Has anyone written a noob friendly guide to DIY on this? If not point me in the right direction and I'll do it. Including, what is that sexy case? nostr:nprofile1qqsxsvs3h524c7mkfe9enw3x8g23mqfqn0n62e4zhvvhrhqmh5ahzhspz4mhxue69uhhyetvv9ujuerpd46hxtnfduhszrnhwden5te0dehhxtnvdakz7qgewaehxw309aex2mrp0yhxummnw3exjmm59e3k7mf0sxguym nostr:nprofile1qqszv6q4uryjzr06xfxxew34wwc5hmjfmfpqn229d72gfegsdn2q3fgpz9mhxue69uhkummnw3ezuamfdejj7qgjwaehxw309ahx7um5wf6k2tnrdakj7qg6waehxw309ac8junpd45kgtnxd9shg6npvchxxmmd9usc5pxf
The case is by PM, not sure he's on Nostr. We have them for sale in the LNbits shop.
We have instructions for the device here https://shop.lnbits.com/nostr-signing-device-nsd-setup-guide