As reported previously (Aug 2018) the GalaPro app from Israel’s GalaPrompter delivers multilingual real-time subtitles (and more) of Broadway shows to your smartphone in the theatre. This accessibility service is now available at the School of Rock musical in Drury Lane, London.
https://www.calcalistech.com/ctech/articles/0,7340,L-3775395,00.html
https://officiallondontheatre.com/news/galapro-app-bringing-theatre/amp/