Change Pseudo-Function Keys to Show/Hide Application

Question

On my macbook air, the F5 key is un-assigned. So in Sparrow I set that key to hide/show Sparrow. Basically I have a dedicated F key to look at my inbox then hide it again to go back to my work.

My question is: How can I re-assign F3 (expose) or F4 (dashboard) or even F12 (eject) to show/hide other apps like Skype, Adium, or VLC?

Sparrow's preferences allowed me to assign a key. Is there an applescript I can write or a Mac System Preferences setting I can manipulate to achieve this goal? I'm open to 3rd-party software, preferably one that doesn't require being in the dock or menubar.

EDIT: I found a handy program FunctionFlip that only changes some of the function keys to their original state. I then found a launcher, Alfred, that I can assign keys to. Thanks to @slhck for the inspiration!

Answer 1

If you want to re-assign system keys such as F3 or F4, you first need to go to  » System Preferences » Keyboard Shortcuts, then check the following option:

Use all F1, F2, etc. keys as standard function keys

Now you're ready to go.

This page gives you lots of AppleScripts to toggle the visibility of apps. Here's one that should work:

set appName to "Skype"
set needsActivation to false
tell application "System Events"
    if frontmost of process appName then
        set visible of process appName to false
    else
        set needsActivation to true
    end if
end tell

if needsActivation then
    tell application appName to activate
end if

You could then use any third party launcher to open it. Spark comes to mind. You can paste the script from above as-is and use F5 as the hotkey:

Rinse and repeat for other applications!