As we have already mentioned in RubyMine Roadmap, the forthcoming RubyMine 1.5 will provide Ruby API for extending the IDE in idiomatic Ruby (no Java or XML). For this purpose the latest RubyMine EAP has built-in RubyMine Extensions Manager for your own extension scripts.
Using Extensions Manager you can enable/disable the pre-installed scripts or add your own ones. Use ‘Add’ and ‘Remove’ buttons to manage your own script folders. Newly added scripts under script folders are considered as enabled by default.
API documentation isn’t yet finished, for now please refer to http://www.jetbrains.net/devnet/docs/DOC-1161. But we will surely get it published before RubyMine 1.5 release.
– JetBrains RubyMine Team