I’ve had this idea for seven years and haven’t done anything with it, so I hereby release it into the public domain and hope someone will make it – preferably an open source version.
Live theater rehearsals rely on actors memorizing their lines. Historically, not everyone learns their lines at the same time. So, for rehearsals, people are walking around on stage clutching bundles of paper, usually with highlighter over their lines.
Everybody has a smartphone now, so let’s use that. This application can be handled in HTML, CSS and JavaScript with a fairly minimal backend for synchronization and distribution. Or you can make yourself unhappy and do it as native apps in every platform you want to support.