Is there a tool to detect log files that have been written to
The console viewer app has bounce notifications in the preferences for that app.



You'll want to open a window with each log you are watching, but this app should cover most use cases of log file watching. Since Console retains window settings when you quit the App, you should only need to open the files once (or worst case, make a folder with aliases to each log you want and open them all from Finder to get a head start on the logs you like to watch). I'll also plug the Divvy tool for managing many windows. Watch the video on their site - it's very powerful if you want to set regions for windows rapidly.