Thanks for the interest, everyone.
A bit more on this....
I'm not really a salesman, and do not really intend to become one - this is strictly as a favour to an old friend.
Seeing that my friend needs some extra cash, and that there are probably a couple of photo geeks around who would benefit from his gadget, I just thought I'd put two and two together.
But, since my friends' English is just barely passable, I realized I'd have to be a mediator, correspondency translator, etc., which is really more than I'm willing to handle, not to mention customer service, manuals, warranties, etc.
So, in short: I'll make the schematics and the screenshots available on a Web page in a couple of days. From there you can make the gadget yourself, if you're electronically inclined. If not, you could purchase a finished one directly from him - the Web page will also have a link to his e-mail.