Well, I was planning to have links to all the correct stuff, and offer a real "offline bundle" for those that donate a certain amount (basically, sending them a set of the cables they need ready-to-go).

The problem with the serial cable is that if they do it wrong, their wallet is exposed to everyone.  They end up with less security than they thought they did, and the false sense of security be worse than not having had the option to begin with (they would've relied on something slightly less optimally secure, but with less user error).

On the other hand, if they do the audio wrong... no one gets to spend the offline coins.  Well, the authorized user will...eventually (even if they have to switch to some other method).  You point out that they could blow up hardware... okay that's a valid risk to take into account here.  

You are clearly more knowledgeable on this stuff than I am.  You seem to think this idea is DOA.  I didn't think it was so crazy, but that's why I put up what I thought was a fairly significant bounty (I'm sure some grad student out there would like the challenge and make some money).

@salfter:

Thanks for that link.  I'll look into it.