Shots like this were inevitably done with a long lens (often a 280 mm or 300 mm f:2.8), and a pair of Motorola transceivers used to direct the model. The walkie-talkie that I used was outfitted with a voice activated microphone from the David Clark Company: (I think that's the name of the outfit that sell all this stuff.) Whenever you see in movies--or real life--people wearing "sickly green" colored earphones (helicopter pilots, et al), that equipment is from the David Clark Company.