SMS Plus PSP now includes the Time Rewind feature I mentioned earlier. To enable it, map any button to ‘Special: Rewind’. The feature alone takes up 85% of PSP’s available memory, and I’m unsure what ramifications this might have for certain configurations, but if you come across problems, let me know.
Approximately 20 seconds of recent gameplay are saved; saving is done once every five frames.
I'm a programmer with too much interest in too many programming languages, and not enough time.