OS X Mountain Lion’s iOS-inspired Notification Center feature lets applications alert you to important events. But there’s more Notification Center could do—with the right apps. For example, if you’ve installed Growl and the excellent HardwareGrowler (Mac App Store link), you can get notifications for things such as peripheral connections and disconnections.

Notifi (Mac App Store link) looks to leverage Notification Center similarly. Like HardwareGrowler, Notifi is a small app that does nothing on its own; rather, it watches your Mac for particular events and then uses Notification Center to alert you to those events.

Using Notifi’s preferences window, you can choose which types of events you want notifications for. Enable the Devices Added/Removed option, and you’ll be notified whenever a volume is mounted or unmounted. (Unlike with HardwareGrowler, Notifi doesn’t watch for all peripheral connections and disconnections—just the mounting and unmounting of volumes.) When a volume is mounted, the notification you see includes information about the size of the drive and how much of that space is currently filled. When a drive is unmounted, you see when it’s safe to unplug.

The Disk Space settings let you set free-space thresholds for up to four volumes. When a particular volume’s free space dips below its threshold, Notifi notifies you. Unfortunately, Notifi is overzealous here: If you dismiss a low-drive-space warning, it quickly reappears. The only way to stop the warning from appearing is to free up some space on the drive (something you may not be able to do immediately) or disable the Disk Space option for that drive.

The Files In Folder options let you configure Notifi to monitor up to four folders for activity. If a file or folder in that folder is created, modified, or deleted, Notifi will let you know. However, it watches only the top level of a chosen folder—changes to subfolders or within applications or OS X packages won’t generate an alert. I also came across what must be a bug: When I added a folder with around 500 items in it, Notifi initially displayed a notification for each item in that folder (though once that avalanche of notifications was over, Notifi properly alerted me only to actual changes). I also experienced an issue where Notifi would sometimes freeze when displaying notifications for that huge folder.

For laptops, the Battery settings let you configure Notifi to alert you whenever your MacBook’s battery level dips below the percentage you choose. Finally, the Time tab offers a number of time-based alerts. You can choose a single daily alert (for example, “Lunch!” every day at 12:15 p.m.); a customizable periodic alert (for example, “Take a break” every 45 minutes); and an hourly notification (just a simple alert on the hour). For the periodic and hourly notifications, you can choose the hours between which your alerts should occur. One issue I had here was that if the ending active time was set to 0:00 (midnight), the alerts didn’t work; setting the ending time to 11:45 (the closest time before midnight you can choose) fixed the problem. I also found that periodic notifications start when Notifi is launched, so if you start Notifi at, say, 2:26 p.m., and you have it set to display an alert every 30 minutes, you’ll see that alert at 2:56, 3:26, 3:56, and so on, rather than on the hour and half hour.

Of course, since Notifi uses Notification Center, you can adjust general notification settings in the Notifications pane of System Preferences: the alert style, how many alerts to save in Notification Center, whether or not alerts make a sound.

Considering the issues I described above, the initial version of Notifi feels a bit rushed. But it also provides a number of useful features that, when ironed out, will be quite handy. I’m looking forward to future updates.

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