To provide some background context, recall the popular news site launched an online TV network in August that streams 12 hours of live footage a day from New York and L.A. It’s a big investment, but the company is hoping its hyper-engaged user community will follow the brand into the video space, and that all that footage will produce buckets of viral content clips to spray across HuffPo and AOL web sites.

So what is the significance of the iPad app in all this? At first glance, not much. The app is simply another way for a user to watch the live stream — which features both ordinary people and celebrity guests like Bill Maher — while reading and adding comments, and sharing shows to Twitter or Facebook. Here are a couple of screenshots that show how comments can appear either stacked or tiled:

On its own, the HuffPo Live app is not extraordinary. Where it could be a real game changer, however, is the fact that the app can be slung onto a TV set using Apple TV. This means that Huffington Post has a chance to control not just a living room’s second screens but also the primary one as well.

In practice, this could occur if groups of friends watch the presidential elections on HuffPo Live and share comments in real time via their iPad — comments that would appear on their TV. If this comes to pass, HuffPo Live will have created what amounts to a walled garden extraordinaire in living rooms across the land.

But could HuffPo actually pull this off? In the short term, the answer is no, as the commenting system is too rudimentary. It allows users to like or flag a given comment but does not let users create a limited community like the ones they know on Facebook or Twitter. A company spokesperson says improved commenting features are coming soon (a Reddit-style up-or-down voting system might be one idea).

Meanwhile, bandwidth will provide another obstacle to HuffPo Live as most houses don’t have the capacity to enjoy an uninterrupted live stream on several devices at once. (Although, as Om’s recent account shows, things are improving quickly).

Still, the future prospects of a living room with a single media source dominating all devices is intriguing from both a user and marketing perspective. Will we one day see other content makers like the NFL or BuzzFeed try to do the same thing?

The “Shadow Conventions” will run online August 27–30, during the Republican National Convention in Tampa, Fla., and September 4–6 during the Democratic National Convention in Charlotte, N.C. The featured topics are “the war on drugs,” “poverty and job creation” and “the influence of money on our politics.” The Huffington Post covered the same topics in the physical conventions it held with grassroots groups in 2000, but this year they are taking place entirely online.

The Huffington Post website will be “taken over” by coverage and its sections will focus on specific related areas. The hosts on HuffPost Live, the site’s newly launched streaming video network, will also offer coverage. “By putting a full-court press on these neglected issues — and bringing the community into the heart of the discussion — we can have a convention that’s unscripted, surprising, and serves as more than an over-produced, tightly controlled political commercial for the two parties,” said Roy Sekoff, HuffPost Live president.

The network launches with ten hosts, “eight hours of live programming out of New York and four hours out of Los Angeles each weekday.” Highlights will be shown overnight and on weekends. Huffington Post reporters, bloggers and editors “will be an integral part of the programming, making regular appearances that will give viewers a real-time sense of what is happening on verticals all across HuffPost.”

Users can weigh in from smartphones, tablets and webcams. Each story is accompanied by a large red record button and “Join This Segment.” Users are asked to explain what makes them “a good guest on this topic” in 140 characters or less, provide contact info and then record their take. Coming this morning are segments about Mitt Romney’s choice of Paul Ryan for Vice President, Arianna Huffington talking about work/life balance, and how gun control measures in Australia could be a model for the United States.

Each video segment is accompanied by a set of “Resources,” links back to “key articles” (both from the Huffington Post and elsewhere), tweets, polls, maps, photos and charts.

The hosts are Marc Lamont Hill, Abby Huntsman, Alicia Menendez, Alyona Minkovski, Nancy Redd, Mike Sacks, Ahmed Shihab-Eldin, Jacob Soboroff, Janet Varney and Josh Zepps. The hosts come from a variety of backgrounds: Ahmed Shihab-Eldin worked for Al Jazeera, for example; Abby Huntsman is the daughter of former presidential candidate Jon Huntsman, and Nancy Redd is an author and speaker on women’s body image and former Miss America finalist.