Thanks, glad to hear it.
I've thought about a hosted app and it's something I'd like to do eventually. The API costs and building a reliable service make it a bigger project though, so it's not happening soon.
Text search is a good idea. It makes reading more active because you pick a concept, see where it shows up and how it fits the structure. The fiction use case you mentioned is similar in a way, finding where a character or concept appears even when the text doesn't use the exact same words. I'll look into it.