Take emojis and stickers offline to real life.
Incorporate into messaging systems (Facebook, Viber, a new app just for this) the ability for users to “leave” messages, emojis and stickers at real life spots in the city. When the recipient approaches the spot, the system will either show him the message or guide him to the place (a game like hot-or-cold) and then show him. The spot can be a meaningful one, or just somewhere the sender knows the recipient will be like on route home.
It would be beneficial in some cases to have a certified publication time for something you published online.
A service you subscribe to, that saves the published content at a given URL with a time stamp. You get a badge that shows on that page certifying the time it was published. It links to the original content saved at the service provider.
Insert a short code in the HTML email that will display your message (or one of several rotating messages) with the seal of approval by the “authority” providing the service.