First, let me apologize for my poor english language skills. (I'm not native english speaker).
I have modified the original source code from NJ CPS1PSP emulator, to add a "rewind" feature like someone of you have tried before on other emulators (like ZSNES or nesDS). To activate rewind you have to press both "R + START".
This release have only been tested on a PSP 1.5 with Harleygs Custom firmware and option "nokxploit = true", so i can't tell you if it will run with other firmware versions, devicehooks, etc.