guck mal in ~/Library/LaunchAgents oder ~/Library/LaunchDaemons ob da noch was entsprechendes rumliegt.

Uninstalling iStat Menus
Simply open up the iStat Menus pref pane in System Preferences, then click Uninstall in the bottom right hand corner of the window to launch the uninstaller.
If you can’t open the pref pane for some reason, you can follow the steps below to run the uninstaller.
Navigate to /Library/Application Support/iStat local/Uninstaller.
Double click Uninstaller to run the uninstaller