"Well, you can't play Duck Hunt anymore with your NES: it doesn't work on modern flat-screen TVs. You need an old, bulky tube (CRT) TV to play. The Zapper can't "see" modern TVs, and modern TVs have enough delay on their inputs to confuse the game. You're out of luck.
Until now.
Do you want to play your...

I wish there was an option to just buy the Zapper mod and use a rom patch instead of the in-line patching module. That would cut the cost way down. But it indirectly encourages piracy which may be a non-starter. I wonder if rom patches will be made for Hogan's Alley, Bayou Billy, and others.
Either way I'm holding on to a CRT just for when I get the urge to shoot some ducks or clay pigeons so I'm probably not the target demo here. It's a very neat project though.