Times have changed and despite customers being ever so difficult to please, they like to catch a glimpse of new products even if they're not ready yet. Call it teasing, science fiction, demo if that makes people talk about you, that works.
|Whatever you demo, make it appealing!|
Give something to your customers regularly so that they know what you're working and what to expect from you. When you're selling something, do not leave anything as a surprise and set expectations early through a nice demo.
Remember demos can be anything, video, blog post, email, just enough to enable people to talk about it!