The iPod/iPhone and the App Store is a great platform for people with ideas: especially the little, fun, "quickie" ideas that agencies are used to coming up with. You don't need the depth of a fully integrated website and social media campaign, you can do something irresistible and silly like iPint.
I think I've devoted the most iPhone hours to a devilish game called Drop7, an addictive cross between Sudoku and Tetris designed by a New York agency called area/code.
What's interesting is that it was originally developed on a website, as part of a promotion for a client. When that promotion was finished, area/code saw the value in the game, tidied it up, renamed it and remade it for the iPhone.
I've seen so many good agency ideas expire when the campaign they were running finished, and so many people lament the lost opportunities that come from not thinking about IP properly. Maybe the iPhone/App Store platform is a place that your fantastic little game can live.
Or there's Jetset by Persuasive Games: designed to satirise the increasingly bizarre and counter-productive security arrangements deployed at airports around the world.
It makes its point by letting you play the role of a security guard implementing bizarre rules and trying to get everyone through to their flight.
The really clever bit is that you can only play in airports - the app knows where you are - and each different airport unlocks different special moves and souvenirs. Makes you think about some of the things you might do with really mobile gaming.
Or there's a lovely little tool called WideNoise, which isn't a game at all, but which, again, points at some of the intriguing possibilities for this kind of interaction.
WideNoise lets you measure the decibel level around you and then place that measurement on a map - creating a loudness/quietness map of your neighbourhood. This is not something many of us would usually consider fun but it turns out to be something you do actually do. Partly because you feel like you're making a little contribution to a social good, partly because it helps you pay attention to the city around you and partly because it fills just those spare little moments of time that gadgets are so great for.
Even if you're not an iPod/iPhone fan, the App Store is worth a visit as a sort of Museum of Darwinian Sorting, and if you think you're good at ideas, maybe it's a place to test them out.