Assistive Devices? Accessibility? What's all this about?
iShowU HD requires access to a feature in OSX known as "support for assistive devices". This is a "accessiblity" feature that by default is disabled. It lets HD see the keystrokes and clicks that you make without it being the frontmost application.
iShowU HD will show a couple of warning dialogs if this option isn't enabled in System Preferences. The two warnings look like:


If support for assistive devices is not enabled, iShowU will not be able to process key presses and mouse clicks as you might expect. We've even seen it cause crashes in the application sometimes. We highly recommend enabling this support (which fortunately, is really easy!).
How to enable Support for Assistive Devices
