Is it possible to launch a specific app when I open a specific finder folder?
You can create a apple script like this:
on opening folder theFolder tell application "BetterTouchTool" trigger_named "test" end tell end opening folder
And save it to this folder: ~/Library/Scripts/Folder Action Scripts
Then you control click on the folder you want to configure and choose services => Folder Actions Setup. Then you select the script.
This will then trigger the named trigger "test" in BTT. (Configure that in the "named & other triggers" section in BTT). Of course you can also directly use folder actions to launch an application using Apple Script, then you'd use a script like this:
on opening folder theFolder tell application "iTunes" activate end tell end opening folder
Awesome, that is what I was looking for.
I'm a Mac user since Mac OS Tiger, and back then, the option of folder actions was already there, but I never really understand what it was for and how it worked. But now I'm a bit smarter.