As the first benefit of upgrading XOOPS 2.6.0, I just ported Debugbar & Monolog Logger to XOOPS 2.5.12
  
Geekwright did really awesome job with implementing it in XOOPS 2.6.0, and I thought that it should be added to 2.5.12 too!
 
If you’re using Ray for debugging, the good news is that the Debugbar module also includes RayLogger that you can use for debugging Smarty templates.
 
 
The XOOPS DebugBar module provides two complementary debugging tools:
 
DebugBar (always available) -- an in-browser toolbar that shows queries, timers, blocks, Smarty variables, errors, and included files directly at the bottom of every page.
 
Ray (optional) -- sends the same debug data PLUS template-level debug info to the Ray desktop app, giving you a separate, searchable, color-coded debug window.

They work independently. You can use DebugBar without Ray. If Ray is installed, both run simultaneously -- DebugBar in the browser, Ray on your desktop. More info in https://github.com/XOOPS/XoopsCore25/blob/master/htdocs/modules/debugbar/docs/ray-integration.md
 
Definitely useful tools for debugging!