As far as I am aware, if your vehicle was built without a seat occupancy detector, the function cannot be activated/retrofitted.
"Once sitting in the front passenger seat, the front passenger is not reminded to fasten their seat belt. There is no visual or audible warning that the seat belt has not been fastened.
With the introduction of option 0230 (additional scopes of equipment specific to EU vehicles), the front passenger seat occupancy detection sensor mat is no longer part of the standard equipment.
The following vehicles do not have seat occupancy mats installed:
F01, F02, F03, F04: manufactured since 01/2010
E81, E82, E87, E88, E90, E91, E92, E93: manufactured since 03/2009
E70, E71, E72, E83, E84, E89: since start of series production
F07, F10, F11, F12, F13, F18: since start of series production
R55, R56, R57: manufactured since 09/2009
R58, R59, R60: since start of series production"
My 2cents, if you are sitting in a moving vehicle, you should not need a reminder to buckle up! :RedNo: