A few days ago I wrote about PS Vita Remote Desktop, a tool that allows you to stream PC games on your Vita, and control them with the Vita.
The author of that application, DigitalArts001 (a.k.a. melfice002) just released the source code for that application on the playstation forums.
One of the “proof of concept” videos that impressed people the most was Left 4 Dead running through this application. If you have an up to date Playstation Mobile SDK, as well as an up to date Vita (yup, you’ll probably need firmware 1.691), and a bit of motivation and/or programming skills, then do give this app a try.