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
Felt for iPhone - Handwritten cards for the modern world
Letter to Yourself - Send a physical letter to your future self
Punkpost - Send handwritten cards as quick as texting
PastPost - Send a letter to your future self