I have read alot recently about iphone apps really taking off.  I guess they sell for anywhere from free to ten dollars, I dont have an iphone yet so I cant comment on what apps I like but I know there are some pretty neat ones out there.  I think theres one that turns the iphone into a wind tunnel or something and a silly one that ifart which is like a digital whoopy cushion.. could be fun.  Some of these developers are making a significant amount of money of these app sales and sounds like there has been a boom in the number of people developing these applications.  So much so that Apple has had problems with keeping up with developer applications.  Everyone wants to jump on this band wagon.  Sounds like you need to invest in the developer contract to sell this at the appstore and get approval as well as needing a mac to develop.  Still some people are making millions apparently and start up companies are focusing strictly on developing these applications.  It will be interesting to see how this compares when the android hits the market with its open source idealogy which should make for some intresting phone competition to Apple.  Im still using my Blackberry untill a smaller iphone comes out :P.