Seems that PSP Dev Wololo has gotten HBL to work on the PS Vita. Here's a example of him playing on the megadrive emulator. It's even working on the new fw.
[youtube]http://www.youtube.com/watch?v=jxjYiEhwqho[/youtube]
Wololo's Blog
[youtube]http://www.youtube.com/watch?v=jxjYiEhwqho[/youtube]
Wololo's Blog