The issue would be if it was made outside the US it couldn't be bought by a regular person even if you wanted to get it classified as an AOW. I doubt it would meet the "sporting purpose" part of the GCA of '68 and without sights and a safety it wouldn't earn enough ATF points as a handgun.
haha wow i want one. i remember this being one of those "please turn your phone off and on for us" things from a few years back. I'd encourage gunmakers to make watch guns(already exist), ring guns(already exist), pen guns(already exist) and even knife-guns(already exist) as much as possible...but not stop there. really they should expland that imagination and make baby diaper guns and roast beef sandwich guns too.