Unlock Angry Birds HD for iPad via the world's first physical in-app purchase

There's a new game mode heading to Angry Birds HD for the iPad, which is exciting news in and of itself. Even more exciting, though, is one of the ways in which you can unlock the new mode. Yep, say 'hello' (soon) to the world's first physical in-app purchase.

There are, in fact, two ways to get your hands on the new King Pig mode, which replaces your avian arsenal with pigs, and your objects of ire with eggs.

Firstly, you can get three stars on all of the levels in the game, which will, of course, take time, effort, and patience.

Alternatively, you can head over to Amazon and buy a King Pig toy, which when placed upon your iPad will somehow magically unlock the content. The only catch is the toy will set you back $12 in the US, and a quite astounding £22 in the UK.

By purchasing this pig, you will also receive a free copy of Angry Birds HD, so if you've not already downloaded it on iPad, you'll be saving yourself a bit of money. You know, in a very roundabout way.

Quite how the magic pig works remains a slight mystery, but we reckon the technical wizardry / hocus-pocus involved may work in a similar way to these Hasbro boardgame / app hybrids and Disney's Cars 2 appMATes.

If Rovio's King Pig physical in-app purchase takes off, expect to see a lot more of this type of thing in future.