You can start a conversation with someone, and talk to them about say, the Saracens, and then have them start wondering how they came about their (small) understanding of them. When they realise it was AOE cutscenes, and that the whole project was a backdoor to deliver historical knowledge to people.
I feel like if you eschew gamification, your audience is largely only those with a deep interest of learning.
I used an app to do a security cert a while back, and it would bug me 3 times a day, and challenge me to test my knowledge. I think it really helped keep my focus on the challenge. Likewise, when I was doing my CCNA years ago, the In-30-Days gentleman, would subscribe you to 30 days of motivational emails to read his book and practice the skills. Not an app, but the same sort of thing.
Some people sell the motivation as the core product, some sell the game as the core product (to deliver motivation) and some people sell the knowledge as the core product. All are valid approaches just make sure you are happy with the market you are targeting.
One more thing: I have absolutely no idea how to obtain calm in todays environment. I dont see myself engaging with an app that requires me to be calm ahead of time, but if it somehow strengthened or created a sense of calm that might be a sufficient product differentiator.