(Aside from the missing 's', I actually managed to fit most of the topic description in this time..)
Finally, Rockstar-style SCM Debugging for San Andreas.
| During the development of GTA: San Andreas, Rockstar North used many features built-in to their scripting engine to aid debugging of scripts. Hacks, hidden modes, teleportation cheats, mission skippers, they had used them all. Obviously these features had to be locked away before San Andreas was released. This mods purpose is to re-implement them.|
Little is known of Rockstars original debugging opcodes aside from what can be found in the GTA IV natives list and their usage within the main.scm and scripts in the script.img archive. However, I believe ScrDebug reimplements most opcodes with near exact functionality (if not, better).
There are several reasons to use this mod. One is that it enables certain "cheats" while playing San Andreas (gaining lives in arcade games, auto-aiming in pool game, skipping missions, increasing stats etc). Another is that, with some edits of SCM, it can be made to output information about SA Levels never before understood (see sapool.log in the ScrDebug folder).
But the best reason is for debugging of your own script mods. You can happily setup debug scripts and leave the debug code in there. The debug code is only enabled for those who have ScrDebug, thus not ruining a mod users gameplay with unexpected happenings. Even if you do want to remove the debug code after, most of these additional opcodes are very handy.