From
grapefruitopia.
To install, just unzip it, copy the clock folder to your storage card, and create a shortcut from the SpeakingClock.exe file to your start menu.
Note that in this current version, the sounds have to be in \Storage Card\clock\ else it won't find them (if the clock just makes beeping noises, then that's why)
There is also an alternative American female voice. I've uploaded both together with a readme file.