Japan's Tomy is making little plastic replicas of American birds that, in an interesting cultural twist, will sing with an American accent. Northern Cardinal, American Goldfinch, you name it. Tokyomango says they're "touch sensory," meaning that the song begins as soon as the bird is handled. (I still like Tomy for the corny basketball-suspended-in-water games it made eons ago.)
Before you invest in one of these plastic twerps, you'll want to select the proper birdsong to match your mood or decor. Check out real calls at Whatbird.com or the best American bird sound library at Cornell's ornithology site. And if you're not into toting around fake birds, you can try birdsong devices like this one from National Geographic.
Then if you really get hooked you may even want to venture outside. But that radical notion may be for advanced birders only.