HMod-InvTools is a project mainly written in ..., it's free.
Invincible Tools for hey0's Mod
A basic tool invincibility plugin, I created this as I noticed lag issues with the existing Invincible Tools plugin.
Ability to toggle invincibility on a per-item basis. Invincibility can be enabled on a per-group basis: 1) Edit InvTools.properties and set "groupPolicy=true" 2) Give the appropriate groups access to "/InvTools" to enable Tools are only "repaired" when their damage reaches a certain threshold.
groupPolicy - A boolean that selects whether enabling is based on groups. Tools - A comma-separated list of item IDs that should be invincible. RepairPoint - An integer that sets the minimum damage an item is repaired at.
Place "Minecraft_Mod.jar" and "minecraft_server.jar" in "hMod-InvTools", load the project in Eclipse, and export a JAR.