Frank, in general you can use the plain Java Client Libraries, Perl, OSLC, REST APIs etc. for all kinds of integrations. What and how and if possible relies more on the tool you want to integrate, e.g. does it have extension points and integration mechanisms, how does it store and make the data available.

However, what and how depends on the requirements and use cases. William created an integration with work items, I think. In general the following things come into mind

• SCM Integration. Should always be possible if the tool to integrate provides a way to export data as a text file. Use API or CLI. It might be impossible to merge data. If the tool itself provides merging,you would have to access the data in SCM and trigger the merging in the tool you extend.
• Work Item integration. Use API, REST/OSLC. You can store UUID's and repository URI information in your tool and locate the work items and their data using them.
• Build. Participate in a build should be possible, If the tool provides some sort of headless build process. Publishing of build data, see https://jazz.net/library/article/797 . See https://jazz.net/library/article/807 for other build related API. You can call for builds, you can contribute data and links to build results.

So the question is what you want to do and if your tool e.g. Spary EA provides you with data and API in usable format and if you can hook up Java or scripts to it.