The invention relates to the provision of apparatus for use in measuring the temperature of a body of matter and in particular the temperature of a foodstuff in a manner which allows the required apparatus in the form of a housing with data processing means and a temperature probe connected thereto, to be used effectively and without the apparatus itself becoming a safety hazard. This is achieved by using materials which are provided in a form to allow the apparatus, and portions thereof to be rendered detectable by metal detection and/or X-ray detection apparatus.