A few weeks ago, Rob Griffiths took a Mac Gems look at Growl, the third-party notification system for Mac OS X. Working as a background process, Growl provides notification services to other programs, letting them alert you in more-effective ways than bouncing Dock icons. When using programs that provide Growl support—examples include Chax, Firefox, Mail, NetNewsWire, SuperDuper, and Transmit—you can choose which events result in notifications, as well as the style and formatting of each kind of notification. For example, if you use Chax, an iChat enhancer, you can configure Growl to display one type of notification for a buddy coming online and another type for new messages from buddies. Like Rob, I install Growl on all my Macs.

But something Rob didn’t mentioned is that the download of Growl includes a number of “extras”—add-ons that provide Growl notifications to other programs as well as for certain system events. Many people overlook these extras, which aren’t installed by default; you have install each of them manually. But overlooking them would be unfortunate, as perhaps my favorite use of Growl is monitoring my Mac using the HardwareGrowler extra.

HardwareGrowler is a simple Growl-enhanced program that, when running—it’s most useful when added to your Login Items in System Preferences—watches your Mac’s FireWire, USB, Bluetooth, and network interfaces, as well as the file system, and notifies you whenever devices or volumes are connected or disconnected. It also monitors your network connections. HardwareGrowler is especially handy for tracking when a server connection is dropped, or for letting you know when it’s safe to actually disconnect a FireWire or USB drive (when you see the Growl notification that the drive has successfully unmounted).

But Hardware Growler also helps you watch out for trouble with your peripheral connections. For example, if you regularly see Growl notifications indicating that USB devices are disconnecting and then reconnecting, that’s a good clue that your USB hub, or one of your USB cables, is having troubles.

These features make HardwareGrowler similar to the discontinued Peripheral Vision, although Peripheral Vision had a number of additional useful features—HardwareGrowler's only built-in option is whether or not the program should, when it first launches, show alerts for every connected device and volume. That said, as with any Growl-enhanced program, a visit to the Growl pane of System Preferences—click on the Applications tab, select HardwareGrowler, and then click on Configure—reveals a slew of ways to customize HardwareGrowler's alerts. For example, for each type of event the program monitors, you can choose the display style, the display priority, how long the notification remains on the screen, and whether or not that notification is accompanied by an audible alert.

(HardwareGrowler is a standard program, so its icon appears in the Dock during use. If you don’t want that icon taking up precious Dock space, the Growl developers provide instructions for editing a file inside the program itself to prevent the icon from appearing in the Dock.)

Though simple, HardwareGrowler is immensely useful. Like Growl itself, HardwareGrowler is installed on all my Macs.

Update 3/5/09, 11:50pm: Added info about customizing HardwareGrowler's notifications using the Growl preference pane. (Thanks to forum member LouKash for the reminder.)

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