For capturing and transmitting live phone calls, apps like mSpy or FlexiSPY are commonly used—they run stealthily on the target device and can stream calls live. These apps require installation on the phone and usually need some initial setup. They often have detection risks if the user is tech-savvy, but they’re designed to be discreet. If you want a quick test, try one with a free trial to see how it works in practice.