ModdedBot is a template for creating a Robocode mod. It provides the interface between the real Robocode, and all the robot behaviour changes you would like to make. ModdedBot extends AdvancedRobot; robots playing your mod simply extend ModdedBot instead of AdvancedRobot, and are then using all the modifications you made. It contains the entire framework for mod initialization and control, and for all event handling; you can do anything you want with events, and not require the robot to rename any methods whatsoever. The template also contains sample code on how to modify events, prevent the robot from receiving events, creating fake events, creating custom functionality such as powerups, and restricting access to certain methods.
To create your own mod, download the template, extract the source code, and rename it and save it in whatever package you want your mod to be in. You can then edit the file to your liking to create anything you would like your mod to do; the source code contains all the instructions you need. Then package up your mod and upload it to the repository, and create a nice little wiki page here introducing your mod and showing people how to use it.
Download it here: http://www.robocoderepository.com/BotDetail.jsp?id=1831
You can also visit TipsToMakeAMod for more information.