Let's say I have an Account object. Suppose one tile updates a field on that Account object. How do I persist that change across all tiles without sending a message to tiles and having them subscribe to it?
The Concepts sample contains five different sample applications which demonstrate various ways tiles can communicate. Besides message passing, tiles can access a context or a resource on the Experience Server.
Installing the samples is described as part of the "Installing ADEP Experience Services" documentation (step 5)
Take a look at the Re: Persisting data across tiles annotation
Under the covers it'll do the plumbing of the event for you. We're still working on a public sample for it.