A mat for protecting a wireless inductive charger having a support surface and a charging area for charging a mobile electronic device located on the support surface in the charging area, the mat comprising:
- a non-conductive or insulating substrate configured to substantially completely cover the support surface in the charging area;
- and
- an inductive proximity sensor embedded in the substrate and including a substantially planar transformer configured to develop a magnetic field in the charging area to detect a foreign object located in the charging area that interacts with the magnetic field.