Is there any PS2 Action Replay or equivalent homebrew allowing user added cheats, or cheat database support? I had a quick look around but nothing major came up apart from people pirating the Datel/CodeJunkies Action Replay stuff.
While I never tried to use it that way, I'm sure you can convert the codes on raw memory addresses and use Kermit for that purpose.
That's right, Kermit includes a cheat engine. Only raw codes are supported at the moment, although most of the code for decryption is present and working (just not being called ;-)). Currently, cheat codes can only be entered via the PC GUI. I plan to include a PS2-side editor in some future version, though.