The author of the text created a React app that analyzes the sentiment of a user's recent tweet on Twitter using Microsoft Azure's Text Analytics API, and then sends an SMS report to the user via Nexmo's Messages API. The app is built with Express.js as the backend server. The author used RapidAPI to connect to the Azure API. The app allows users to input their Twitter handle, retrieve their most recent tweet, calculate its sentiment score, and send the result to their phone number. The sentiment analysis is based on a numeric scale from 0 to 1, where 0 is negative and 1 is positive. The author also added some logic to analyze the sentiment score and assign an emoji to it.