Gaia

Gaia is a personal assistant you run on your own computer and use from your iPhone. It keeps your conversations, memory and schedules on your computer, and can work with your mail and calendar when you connect them.

Your computer, your data. No server run by Gaia's developer receives your data.
Mail and calendar. Gaia reads your Gmail and Google Calendar on demand, for your briefs, your invitations awaiting a reply, and your conflicts. It keeps no mailbox copy.
You approve every action. A send, a draft, an event change, or a reply is a card you approve first.