Version format update; it's now "YYYYMMDD" with Y being the year, M being the month and D being the day of the last update (in GMT). A number (hour/minute) will be appended if there is more than one update in a day counting the number of additional updates.
This hack modifies {checksum protected code} to load (code) which hooks [code which is executed each frame] to code stored at the end of the ROM outside of the {checksum protected area}.
The hooked-to code then loads a "cheat list" from even later in the ROM and processes it each frame, just like a GameShark.
Because of how this system works, it can be used to create ROM hacks which apply cheat codes, but the cheat code format is enhanced and custom made. It does not match the same cheat code specification the GameShark uses but rather improves upon it significantly.
Source and a completed sample hack is included. There is currently no support for TLB codes though it should be trivial to add it due to the readily update-able nature of the implementation of the hack (since the trainer code and "cheat list" are both expected to be stored outside of a {checksum protected area} and are stored in the ROM and loaded into the RAM at locations with several kilobytes of free space).
The latest version of the hack (at least from the original author) can always be found
http://dl.dropboxusercontent.com/u/336940/Distribution/Jet%20Force%20Gemini%20Trainer.7z.
The way the trainer loads seems to require implementing hacks to have register caching disabled for the ROM in Project 64. Other oddities of using the trainer such as graphics plugins not recognizing the ROM and which settings to use are noted in the various README files throughout the release.
Also note that implementing hacks may not run in the interpreter mode of Project 64, although the recompiler core works fine (and runs faster anyway).
The sample hack which is included is a fully operable hack for playing through the game's single player mode with more than one player as one of the Jet Force team members (as opposed to Floyd) with support for up to 4 players.
There are instructions for getting the hack working both offline and online included.
If you are having problems with the hack, check for updates often as I am doing a second playthrough of the hack to round up any information about it I may have missed the first time around and regularly update the documentation as I find things.
Jet Force Gemini (USA).n64
CRC32: B5932174