A developer built an SMS app using Python and Twilio that can retrieve stock prices via a simple HTTP request, allowing users to check stock prices with limited mobile connectivity. The app uses Flask as a microframework, requests for making HTTP requests, and the Twilio helper library to send and receive SMS messages. After setting up the dependencies and creating a basic route, the developer modified the code to include a URL parameter that allows users to request specific stock symbols, retrieve their prices from the Yahoo Finance API, and display the results in an SMS message. The app is then exposed via ngrok to a public URL, allowing it to receive incoming SMS messages from Twilio. With this simple app, users can quickly check stock prices on their mobile devices using only a few bars of signal strength.