Some new details are trickling in about the rumored Apple HDTV, courtesy of the blog Cult of Mac, which says it has a source that has seen a prototype. You know the drill: file this under “rumor”–albeit a somewhat credible one.

The source says that the prototype he’s seen looks like “an Apple monitor, only much larger”–namely, something like Apple’s Thunderbolt Displays, which employ LED backlight technology. (“Stunning is an understatement,” Apple’s site says modestly of the 27-inch widescreen version.)

Cult of Mac’s source also said that the TV integrated an iSight camera for FaceTime video conference calls, and that it used Siri, of iPhone 4S fame. Here’s the coolest rumored spec of the iTV, if I may call it that (and everyone is): facial recognition technology that can follow a user’s face and zoom in on it as she moves about a room. No more needing to reposition your webcam, or to hold your head rigidly in one place when making a video call: the idea is that your camera would do that for you. (In February, a report in Canada’s Globe and Mail suggested that the iTV might also be activated by hand gestures, and provide access to sites like Twitter and Facebook.)

Novel technology, but how credible are the new rumors? Kudos to Cult of Mac for giving some context about their unnamed source. As they write, “Our source is well-placed and has provided us with great tips in the past. However, not all of them have panned out, ostensibly due to the fact that our source tends to see products in the prototype or early development stage and Apple doesn’t always ultimately choose to release them.”

Cult of Mac’s source had no word on pricing or release date. In late December, rumors emerged that the iTV might come out as soon as 2012. But a few days ago, a J.P. Morgan analyst put the kibosh on that idea, or at least its wisdom. “We are not sure that the Apple premium could prevail in the TV market, unless there is a radical change of the user interface, integration of the TV programming and data content, and use of gesture or voice control,” Mark Moskowitz said in a note to investors. He foresees, instead, a two-phase plan, where Apple first revamps its set-top box in 2013, and only then brings out a proper iTV in 2014. The TV market is simply too “strained,” he wrote: “Overall, we would be surprised to see Apple enter a new market unless the value proposition could support double-digit operating margins. In TVs, that bogey is rather elusive, in our view.”

For all the excitement over an Apple HDTV, I’d like to return to two points I’ve made here before. The first is that the TV–simply in terms of its hardware–is pretty much as developed a technology as you can get. Most innovations in TV hardware–ultrathin, 3-D–have been some combination of gimmicky, expensive, and unpopular. (See, for instance, “Would You Pay $8,000 for a TV?”) The second point is derived from Wade Roush of Xconomy, who was himself inspired by a post from Mark Sigal: it’s that for Apple to truly innovate in the TV space, it would need to produce a killer TV app, not a killer TV screen. Our TV sets are working fine; it’s television as a category, and the myriad ways we access it (or fail to), that’s the real Gordian knot in need of a cut from Cupertino.