Do not try to buy all sorts of Bluetooth devices to record conversations, but only if you do not mind their money! Prices for these devices are inflated many times, but there are cheaper and better ways to write it. This requires anyone with a cheap digital recorder with a line input or external MIC and able to listen to the signal from the input to the headphones in real time, most Chinese recorders for 20-30$ it can. Next, we need a cable with 3.5 Jack on both ends, one plug in the iPhone, the second in the input of the recorder, the recorder plug-in headphones and all, the design to record ready. iPhone thinks headphones are plugged in to it and when you make a call all sound (including your voice) will transmit on the input of the recorder, the recorder will take notes and all you hear in the headphones. Conversation will use the standard iPhone MIC. It is clear that such construction is not always convenient to use, but it is no different from devices that connect as a headset and record your calls..