You've read already about Heirloom items, which were implemented in the latest beta build and are bind-to-account. You can equip them, and then when you get a replacement, send them to any alt you have on the server; the stats on the items scale with level. They're bought with heroic/raid badges, as far as I can tell.
In Wrath of the Lich King, Emblems of Heroism are one of the Badge of Justice equivalents. They're acquired through beating Heroic bosses and 10-man raids. Currently 25-man raids award Emblems of Valor, which are not used for any Heirloom items.
Unless you're a chronic altaholic, you may want to hold off on buying these Heirloom items, because there's also a wide variety of epic gear you can buy with it that's Bind on Pickup. Again, these are the Badge of Justice equivalents. Think of the Heirloom items like the epic gems or Nether Vortices from The Burning Crusade. If you want to gear up your main, these items are going to be things you buy after you have nothing else left to buy. If you spend most of your time leveling up alts, these items may be very good for you to buy right away. These items are called Heirloom items, or Bind to Account (BoA) items.
They aren't tied to any one character and can be freely passed from alt to alt, but they're all tied to one account, the account that bought the item. No handing them over to your friends, no mailing them to other players, no mailing them to your second account. So far none of these items are drops, but rewards for more veteran players of the Wrath content. There are two different ways of earning these items, but they dovetail nicely.
Quite simply, you need to participate in Wrath's content. Items suited to PvE are acquired via Emblems of Heroism, and items suited for PvP are acquired via Stone Keeper's Shards.
So what are these items for? My interpretation is that they're largely to help your alts level, and to give you something to do with badges if you have too many on your mains. Although the stats do scale down when you equip them on lower-level characters, they're still quite powerful items, on par blues. And here's one thing that's reinforcing that impression: I've found four Heirloom shoulders so far that give +10% experience from killing monsters. This is a great idea. You know that anyone who has these shoulders has at least one character at level 80, so why not let them level 5% faster? (5% is based on an estimate of half of one's experience being from quests and half from mobs.)
There seems to be a set of +10% experience shoulders suitable for every class and spec. Armor type (leather/mail/plate) will vary as appropriate for the character you equip them on, as far as I can make out.
It's really nice to see old models return. I expect we'll see very many of these shoulders on sub-80 characters in LK. I'm excited to be able to level my characters that much faster; I've spent more than enough time in Azeroth at this point. As Zach pointed out, Heirloom gear puts the emphasis when leveling on getting levels; it discourages going into dungeons and pursuing drops. Not that I do that these days anyway.
The PvP focused heirloom items technically don't require you to PvP at all, but it speeds up the process. When your faction has just won Lake Wintergrasp, your entire faction gains the Essence of Wintergrasp buff. If you're familiar with Spirit Shards from The Burning Crusade, it's more or less the same thing. You loot the Stone Keeper's Shards from bosses in dungeons while you have the faction-wide buff. You'll typically get 2-3 shards per boss, in both normal and heroic versions of the dungeon.