That is very nice. Even if I do not run a paysite myself now, I was asking about something like this earlier, also the "invisible fingerprint", and content protection is obvious market these days, when producing something new. I mean, who wouldn't pay some few bucks for protection if they can gain hundred or thousands times from it?
You should market it, and I will surely forward it if you do
The only problem I see, is if someone get their member account hacked, or "pretend" it is hacked. But the IP part could do the trick, together with properly tracking software. At least limit it, and make paying members think twice before they upload to rapidshare or whereever they share.