Here's a quirky story: Israeli iPhone app dev house ApParty released an app back in December 2008 called iFog (iTunes link). The premise being that the user selects a photo which then has a steam effect superimposed upon it. The steam can be wiped away by running a finger over the screen surface. Blowing on the iPhone microphone fogs the screen back up. Cute. Simple. And lucrative—it was bought 200,000 times for $0.99 a pop.