A Simple Solution. An almost Apple Watch exclusive social experience.
Bottle, an experience completely within the Apple Watch, lets you create a "message in a bottle" from the Apple Watch and send it to another random user, who can then pass it on if they choose.
The main UI happens on the Apple Watch. This includes message composition, and access to the last message sent to you. You can "Pass It On", meaning putting that message back out into circulation for someone else to catch. You can create a new message to release into circulation.
You can "Pass It On" from any notification UI, but the real magic is containing the experience to be fully accessible on the Apple Watch, and to have as little as possible on the iPhone app.
A Theory in Concept.