The PSP Trainer for "Liberty City Stories" has been updated. For now it already supports a few basic cheats like: Infinite Health and Armor, Set Wanted Level, Set Time, Set Weather & Spawn Anything. This trainer in it's version 0.1c works on the US/Canada version of LCS and requires a 2.0, 2.01 or 2.50 firmware. Version 1.0d seems to work only with the UK version of this game.
Unzip the archive to your memory card so the files go in PSP/SAVEDATA/ULUS10041S0 if you're installing the US version, PSP/SAVEDATA/ULES00151S0 for the UK version. This replaces the first save on the card. To start CheatDevice, simply load it like a saved game. You can then load another save if you want and CheatDevice stays in memory.
Disclaimer: THIS CAN CRASH YOUR GAME. USE AT YOUR OWN RISK. Some of the spawn choices like the RC toys and boats will crash the game. Don't save your game after using this.