Hooks Manager module
The Hooks Manager module provides you with a simple interface to add your own code or HTML/Smarty markup allowing it to appear in Form Tools pages, or have it executed at particular junctures in the code. What code you choose to add depends entirely on your needs.
Form Tools has dozens and dozens of "hooks" littered throughout the code and within the Smarty templates used to generate the visible webpages. These allow developers like yourself to develop modules that extend the core functionality and display extra information in the UI.
Like to add new fields to any of the Form Tools pages? Like to send emails to notify yourselves when specific users change specific values in the form submissions? Like to know when users are exporting data? No problem! All of this - and far, far more, can be done relatively simply by using this module. To give you another idea, from a technical standpoint the entire functionality offered by the Submission Pre-Parser and Extended Client Fields modules could be emulated using the Hooks Manager. They were implemented as separate modules since they're easier to handle that way.
Read the documentation for more info.