EteSync

EteSync offers secure, end-to-end encrypted sync for contacts, calendars, and tasks. Works with Tasks.org and OpenTasks. Requires an EteSync account (paid or self-hosted). Easy to use, integrates seamlessly with Android. Zero-knowledge encryption ensures privacy—even we can't see your data. Full history with encrypted, tamper-proof journal. Visit https://www.etesync.com/ for details.