The Guild of Calamitous Intent`, a team of three developers, Imran, Fahm, and Shahriar, won the Rails Rumble's Grand Prize with their app `Rumbler`, which tracks customer feedback by recording and transcribing calls via Twilio Voice and analyzing sentiment. The team built the app in just 48 hours to provide actual value to businesses by visualizing trends and identifying areas of improvement. They prioritized their core feature, focused on integrating Twilio's API, and created a beautiful UI with Fahm's creative design. After being announced as the winner, they received positive feedback and support, and plan to release Rumbler beta in a few weeks.