Download Lockdown In-Game v1.0 : http://ifile.it/le120ys
Lockdown In-Game will require you to enter a password when you resume your PSP from suspend mode. Useful to prevent other people from messing up your progress if you put the PSP in suspend during a game.
Put it in the ms0:/seplugins/ folder and make an entry in GAME.txt (e.g. ms0:/seplugins/lockdown.prx).
It is recommended that it should be the very first entry in GAME.txt (How ever if you also have Hold+ installed, then make Hold+ first and lockdown.prx second).
Use the included exe to create a password file (buttons.ini) and put it in ms0:/seplugins/
If you also have the flash0: version of Lockdown installed, then this will detect and use the same flash0: password.
It only works in GAME mode. It will not work in the XMB.
I have only tested it with few games that I have. Its recommended that you don't suspend the PSP while a game video is playing as sometimes it doesn't work properly during video playback.