There I was twiddling with Game Maker when all of a sudden Unity pops up with a blog post, announcing the public preview of Unity for PSM. It allows any Windows user to code for PlayStation Mobile with no fees required. You might need to buy a copy of Unity after the preview, but with the race to free for development environments, probably not.
Unity for PSM gives potential coders full native access to PS Vita as well as full access to PSN. As part of your dev kit, you also get a comprehensive suite of performance and native debugging tools, Visual Studio integration and Razor CPU/GPU performance tools. Get started here. The full package will hit this summer, so you've got some time to become a coding ninja.