The email encryption options on mobile are laughable at best, and we hope to make a positive impact in the space.
Our Android app is ready for private testing. If you'd like to try it out,
please write me through my encrypted contact page and I'll send you a link to the early testing version.
Update February 2018: see FlowCrypt Downloads to download our Android app
iOS is also planned later this year, as well as desktop apps for Windows, Mac and Linux. These will support Gmail, Outlook and any other email provider out there (while browser extensions are designed to only work with Gmail).