hehe, true about the kernel extension vs. a checkbox - but it's the 
only way to give the user some functionality and work around bugs in 
Apple's code they don't seem to feel like fixing themselves ;-)

In fact, though, enabling support for assistive devices support is 
actually far more scary, as it allows any app to get all key presses 
you perform on a low level, opening up a huge security hole, because 
then any app can - without you noticing - log your keypresses. There 
isn't any malicious software for OS X I know of, but from a security 
standpoint, it's something to keep in mind.

Excellent idea with the floating icons. Not hard to do at all and 
definately an idea I like a lot! There's already the "legend" to help 
you out with the current mapping (I actually use it a lot with apps I 
rarely use), but a default visual confirmation certainly is a good 
thing to add, still.

Best regards, 
Felix