I finally found out how to use this app properly! This is what I did : I have a French AZERTY layout on the keyboard, but on the "Physical Keyboard" section of my settings, I chose the English (US) layout (don't ask my why I this works, I don't know...). And then, I chose the French layout for this Belkin Keyboard Extention and it worked! Problem solved :)
I have the F5L170 keyboard. This app gives the wrong keys for various signs such as the @ and the pound sign. Neither of the other two Belkin character apps, which claim to fix bugs, solve this problem.
Added compatibility for the Mobile Wireless Keyboard (F5L175)
This is the official Messaging application for your Sony smart accessory.