Sony announced today that it has opened up its "Unity for PlayStation Mobile" tools as a public preview, and will be launching its full official version sometime this summer. With this, Unity developers will be able to port iOS or Android games to PSM without paying extra charges, letting them essentially release them on Vita for free (minus platform frees, of course).
The announcement promises more improvements to be made throughout the public preview version of "Unity for PSM," and a full official version will roll out sometime this summer. The goal is to make it easy for developers to port their iOS and Android games to Vita using the Mobile tools. A "PSM Developer Program" will begin on May 29. You can register through the official site.