After searching at length for a Joomla component that automatically adds links and tooltips to keywords in articles I couldn't find anything that suited my needs so I decided to develop the extension myself and learn a new skill at the same time.
The result is the Autolinks extension for Joomla which has been released today. If you are interested in using this extension it is free to download and use.
Developing this extension has refreshed my PHP programming skills and has taught me a lot about developing components and plugins for Joomla which is a skill I can use wherever I am so long as I have access to the web.
The bonus is that this is something I actually enjoy doing and am already planning enhancements to Autolinks and a number of new programming projects.