I don't think it occurs to many people to seek out and use memory tools. However, there are groups of people who do have a very specific need for these tools and actively seek them out. I'm thinking of people like medical students, language enthusiasts, etc... Anyone who has an immediate need to learn and recall large amounts of information.
By intentionally limiting the scope of what you offer, you can better target prospects and tailor your offer to fit their needs like a glove.