- Opal: $20/mo, $100/yr, $300–400/lifetime (4.7/5 stars with 6.1k ratings)
- one sec: $4/mo, $15/yr, $40/lifetime (4.9/5 stars with 6.2k ratings)
- ClearSpace: $7/mo, $45/yr, (n/a?)/lifetime (4.7/5 stars with 404 ratings)
In the thread you've addressed some current features differences already (progress / streaks tracking, and pulling one out of an app after a set time limit).
Are there specific things you want to do differently in the future than what those apps do today? [They appear to be going in two very different directions.]
[1]: https://www.opal.so/
[2]: https://one-sec.app/