Alexa vs Tropo: What are the differences?
Alexa: A cloud-based voice service *. It is a cloud-based voice service and the brain behind tens of millions of devices including the Echo family of devices, FireTV, Fire Tablet, and third-party devices. You can build voice experiences, or skills, that make everyday tasks faster, easier, and more delightful for customers; *Tropo:** Add Voice and SMS to Your Applications. Tropo is a powerful yet simple API that adds Voice and SMS support to the programming languages you already know.
Alexa and Tropo belong to "Voice and SMS" category of the tech stack.