Handwrytten - Handwritten notes straight from your device. Huge selection of cards or design your own. Handwriting service integrates with 1000's of apps.
Future Me - Send an email to your future self
Handwriting.io - Real handwriting without the pen – no robots, all software
Letter to Yourself - Send a physical letter to your future self
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.
Felt for iPhone - Handwritten cards for the modern world