A very good safety device, but the beeping is so annoying (eg when moving a trailer around & need to take safety belt off).
But it can be disabled!  the same system as applies to Fords works - simply turn ignition on then rapidly (within 1 min) put the safety belt in & out of the clip 9 times! On the 9th time the safety belt light will stay on for a while & then after that you still get the safety belt light but not the "beep" One caution... I don't yet know how to re-enable the "beep" 

Source: disco3.co.uk  

I have verified this yet on my MY07.