This discussion on the list is great. But it might also be useful to maintain (using some web tool, but not on mail list) a simple, short "Password Safe Requirements" document.
>> Project description, including
.. what problem the password safe solves
.. what sort of person will buy the device
.. what the device will do and general characteristics, (but NOT how it is implemented)
>> rough cost targets
low quantity (n~= 100)
modest qty (n~=1000)
>> target date for first proto
>>NON-goals for project (optional, but can be useful)
If you sorta kind like the idea, I volunteer to create the document based on your input.
There are a few web systems designed for collaborative writing, often using Markdown syntax for formatting.
IMO it would be harmless and possibly instructive to experiment with something like that for this brief document.
This is a marketing rather than an engineering document. It is about what is needed by the target customers.
These requirements are already known, but have evolved over multiple messages in the email flow.
As (many...) more people become aware of this (rather cool!) project, having a single solid starting point for current requirements could easily be worth the effort.