Bukkit

• It is now possible to define which worlds the plugin affects, please see the config file to enable it on your world
  
• Implemented caching of irradiated blocks and added support for Hotspots.
  
• Added metrics to track plugin usage, you can opt out by editing plugins/PluginMetrics/config.yml
  
• Made Geiger command/item return more human-friendly numbers.
  
• Fixed a bug allowing radiation to injure players in Creative mode
  

Hotspots are not actually active yet, they will be active in the next version.