I have an opinion, since it's an iOS application, should we follow Apple's Human Interface Guidelines
For developer we may export as a png.
Also mock-up as App, Spotlight, Settings, and Notification Icons all in one. Like we are going to propose to a real client.
I'm guessing if someone who puts these much extra effort, probably wants to see his work alive. So it may increase the amount of interaction with project owners. It's not end up dead in utopian's history. And of course same as Androids and Windows Mobile if they had a guideline which I've never seen before.