The solution is rather trivial – and also very simple to achieve.

Open the System Preferences application and choose Keyboard & Mouse then change the Keyboard Shortcuts option to “All controls” (this can also be toggled using Control-Function-F7 if you are so inclined).

You can now use the tab key to cycle through checkboxes (use the spacebar to select a checkbox when you have cycled to it) and radio buttons (you can use up/down or left/right arrow keys to toggle a radio button when the group is in focus).

A similar option is available in Safari (MacOSX as well as Windows) in the Preferences menu option (within the Edit menu). Select the Advanced tab and select “Press Tab to highlight each item on a webpage”. When enabled, this option allows you to cycle through all elements that can receive focus using option+tab (this includes standard links on the page as well).

I’d like to credit this “discovery” to Brad Jasper and Dylan Ryan at MacTips: Tips & Tricks – but the post is no longer available. Thanks for the heads-up guys!