Works on some sites, doesn't work in address bar, no way to configure which sounds it actually plays.

The extension is safe; not a keylogger or any sort of that. The backspace and enter keys work fine. However, keys, such as (well, the alphabet) does not work. After taking a quick look at the source code, the dev has not spelt keypress correctly. Well- he did, however, instead of "keypress1" it needs to be "Keypress1". Just some minor things you could fix ya'self.