Caco3,

Using "dbus-monitor --system" in the terminal, received these signals:

1- signal sender=:1.9 -> dest=(null destination) serial=1553 path=/com/nokia/mce/signal; interface=com.nokia.mce.signal; member=display_status_ind
string "off"

2- signal sender=:1.9 -> dest=(null destination) serial=1556 path=/com/nokia/mce/signal; interface=com.nokia.mce.signal; member=display_status_ind
string "on"

Signal 1 when display off, and signal 2 when on!
Register in dbus listening these signals and be happy!