Users who upgrade their iPhone to iOS 8.3 when it's released next month will be finally able to tell Siri to make a phone call through the device's speakerphone when the 'Hey Siri' option is enabled, reports 9to5Mac.
You can say, for example, 'Hey Siri, call my Mom on speaker' and the call will be automatically transferred to the iPhone's speaker, like it should have always been, may I add.
Again, provided the 'Allow Hey Siri' option is enabled in Settings > General > Siri and the phone is plugged into power.