Mu4e - Starting with version 0.9.8, mu provides an emacs-based e-mail client which uses mu as its back-end: mu4e.
Glympse - Glympse is the easy way to safely share your location in realtime. No sign-up needed.
Mutt - Mutt is a small but very powerful text-based mail client for Unix operating systems.
OwnTracks - Cross-platform location sharing
Mailspring - Mailspring is a mail client for Mac, Windows and Linux.
Mapple.me - Mapple.me bridges the gap between available time and availability of friends to increase social...