We're excited about this - the South Park team are developing what looks set to quickly become one of the most downloaded applications on the App Store, the South Park iPhone app.

This app will grab clips, wallpapers, South park-related news and even lets you use South Park characters as pictures for your contact book. As reported by BoingBoing the application won't let you download and stream full-length episodes, so you'll have to use iTunes to buy and YouTube to forage for those (and don't forget all South Park episodes are available legally online), but it looks great, and we think it will be really rather popular.

We also know the application has been submitted to Apple and "hopefully will be made available soon", the South Park people said. Recent weeks have seen the delay between submission and arrival on the store pan out at around seven days, so with luck we should be playing with this app come next week (It wasn't available at time of writing).

Naturally, there's a serious side - this kind of interactive experience is becoming a growth industry for marketing people, with a host of companies seeking to emulate the Audi driving or iPint experience by offering a little dose of iPhone fun beside their brand. Kind of "friendly advertising", which they hope we'll be less resistant too.

And it seems this kind of mobile advertising's emerging as THE growth sector, according to a report on CNN. That report says the mobile ads market's about to grow into a $12 billion business by 2012, up $10 billion on what it's worth today. T

hat's a lot of cash to divvy out between savvy iPhone application developers. And if you want to get more savvy, Apple announced a world tour for developers this morning - check here. Now get building, even in this recession there's an Apple-inspired Gold Rush on...