Custom Photoshop Tool

Is it possible to create a custom tool and add it to the toolbar on the lefthand-side toolbar, and use the tool to communicate with a CEP panel? I have not seen any documentation about this.

Assuming this is not possible - would a viable alternative be to create a modal dialog (triggered by an event in CEP panel) where I could override an existing tool (like pen or brush) and send results back to the CEP panel achieve a similar result?

Here's a great example of a similar use case, where the cursor in a modal dialog becomes a brush-like tool that selects colors: https://github.com/smallpath/adobe-color-picker
Looking for ideas on how to approach a "custom tool" like functionality and tying it to a CEP panel.