The extension uses cURL (command line, not the PHP library) to connect securely to the NHS email servers, making use of the NHSnet SMS gateway to send SMS messages. Probably only of use or relevance to CiviCRM users who are working in NHS organisations in the UK.
Features: smtp transport, server (peer) verification using public CA certificate,
Tested, working for us. YMMV. It's a work-in progress. Happy to discuss additional applications, and use cases.