Fully On-Device Period And Fertility Tracker That Never Phones Home, For Users In Post-Roe States Who Refuse To Trust A Cloud
Three years post-Dobbs, the major period-tracking apps still share data with third parties (87% per Privacy International's 2022 audit, with no public reaudit improvements in 2026). State prosecutors have publicly indicated period app data could be relevant in abortion-related cases. Users in restrictive states want a tracker that lives on the device, encrypts locally, and has no account at all - not just 'we promise' marketing from Flo. Ship a true offline-only tracker with optional E2E backup to the user's own iCloud or self-hosted Nextcloud.
This is a marketing-and-trust product more than an engineering product. Ship the Drip codebase forked with a privacy-audited story, get an actual third-party audit (not your own), and put 'no account, ever' on the home screen. The users you want will pay $10 to know exactly nothing about them is on a server.
landscape (5 existing solutions)
Drip already exists and is open-source, which means the real product gap is polish and a credible privacy-marketing posture, not raw functionality. The opportunity is to take Drip's architecture, ship it with a 2026 UI, an on-device LLM-explainer for cycle questions, an explicit no-account default, and optional E2E backup to user-controlled storage. Charge $10-15 once. The market is users in restrictive states who are paying for VPNs and Signal already.