Carddav support would a huge win. Even some sensible markup to store metadata in the notes field could allow some kind of editing on the go, and synchronization.

I'll be watching your github repo / release notes pretty closely - will try and make a simple people / event entry + reminder only mobile app for my personal use (and for others, if there's interest).

If you made a solid API, I would be very interested in developing a react-native app.. :)

An API would definitely be a positive step :) awesome work!