Not only cross platform but cross service. The real loss in messaging in general is the lack of interoperability. One thing email did get right - protocols. The messaging wold seems to have given up on this to hoard and lock in users to silo'd messaging systems - wechat, snapchat, fb messenger, etc. How powerful would it be for people to have the ability to send messages across these systems <i>with</i> the support of these vendors (as opposed to the Trillian like solutions of the prior decade).