Letter to Yourself - Send a physical letter to your future self
Phonebot - Make phone calls from within a Slack channel
Future Me - Send an email to your future self
ShareAccount - Share your account without giving out your password
Letter to my future self - Letter to my future self is a prominent email scheduling service that gives you the opportunity to create a letter with goals and thoughts for your future self and schedule a date for sending it.
Wing-project.org - WING - Wireless Mesh Network for Next-Generation Internet