Briksoftware has introduced FNable 1.0, a productivity app for Mac OS X 10.6 or higher. It costs US$1.99 and is available worldwide through the Mac App Store in the Productivity category.
FNable serves as the caps lock for your FN key. It runs in the background and can quickly change your special keys to function keys. The applications that use function keys are remembered; every time you switch to such an application, the function keys will be available. While you can add FNable to your menu bar, you can also place it in your menu’s corners.
You can still use the special keys while your function keys are active. Just hold down the FN key when clicking the function keys.