LVM: Just call external script/URL with parameters for user notification (or another purpose).
For example, at ticket creating call URL

  blah.dot.com/cgi-bin/reminder.cgi?project=%p&action=%a&data=%n

or execute this script

  /bin/reminder --project "%p" --action "%a" --data "%n"


Where %p - project name, %a - action (ticket created/ticket changed/wiki page edited/etc), %n - ticket number (or checkin number or Wiki page name or ...).