The Twilio Presence feature allows developers to receive notifications whenever the availability of any of their Twilio Clients changes, making it easy to implement and use in existing apps. A developer contest is being held, with a grand prize of an 11-inch Macbook Air, where participants must submit their app using Twilio Presence by October 30th, with bonus points for submission to the App Gallery or use of Twilio Connect. The contest aims to encourage developers to build something awesome with Twilio-powered solutions, providing resources and support through forums, documentation, and webinars to help them get involved.