The present invention relates to data acquisition and transmission apparatus 10. The data acquisition and transmission apparatus comprises mobile apparatus 22 that is configured to be attached to a beast 20. The mobile apparatus 22 comprises: data acquisition apparatus that configured to acquire and store data and wireless data communications apparatus, which is switchable between an operative condition, in which stored data is transmitted wirelessly, and an inoperative condition. The mobile apparatus 22 also comprises a trigger receiver configured to change the wireless data communications apparatus from the inoperative condition to the operative condition in dependence upon a trigger signal.
