StatusNotifier, the utility that allows you to display small icons on the StatusBar, in order to notify us of receiving a new message, a missed calls, unread e-mails , and messages from various IM, has been made compatible with the 3.0 firmware but it is not yet available in Cydia as it is in a stage of Beta Testing. If you want to test it , here is what you need to do:
First you need to download iStatusNotifier.deb and use this totorial to install or copy the deb file to /var/root/Media/Cydia/AutoInstall , than reboot AND respring your iPhone.