The US Army, together with several universities and companies, is funding research into the Internet of Battlefield Things (IoBT), a project that aims to optimize networked devices for military use. Echo REIGN is an Amazon Echo customized by artist Wesley Goatley to approximate how a US Army battlefield-standard Echo might be designed. Through the headset, Echo REIGN responds to your commands using a special interface optimized for combat environments rather than for shopping.
Part of the agreement that Echo users sign says that Amazon can use their data and interactions (including ones such as yours with the Echo REIGN) to develop and refine new products. This includes the voice-user interface, which is being constantly trained by millions of real-life interactions between Alexa and its users. Amazon has been able to use this data to produce versions of their machine learning systems (like speech recognition) for the IoBT project. Would you think twice about asking Alexa if you knew your interactions were helping to train military technology?