This flow diagram describes how a user views a default Ad and increases her balance, but more importantly how Ads are presented in an non-intrusive way. The design challenge is how to present Ads everywhere in the application without making them a nuisance. The solution given here places one Ad as the first item on every list, however the Ad is not selected by default. In this way the application behaves as if there were no Ads, i.e. the user does not have to skip the Ad every time a new list is presented. But she can still select the Ad if she is interested in the product. I think this is a very simple yet powerful solution to this problem.

This flow diagram describes how a user would record a Karaoke ring-tone. One implementation restriction is that the user records his/here voice by making a phone call to a specific number. The backing music is played for the user during the phone call. If I were to design this service I would do the recording session locally without a phone call.
Another functionality displayed here is how the user pays for services using his/her credits earned by viewing Ads.