New processes

What ways there is for script to get message, when any new process launches?

Have an on idle polling the system events. Either just the count. Or check previous processes names list with new name list. Any Change activate your script.

If you just want to block Applications, use parent control. You have to be log in as a non admin user.

Trigger on events can be setup with Cocoa or C, Out side my skills.

Good luck.