For example we have a web app that syncs audio on any device running safari or chrome. When we demo/ turn a crowd and their devices into a stereo..we just ask them to go to X URL.
They load it up in their device and the host hits play. The audience is not forced to download an app and do a few other steps. It's just load URL and bam everyone's devices become a stereo. Many other ideas in this space can occur.
The web and what you can do it with current day isn't as hobbled as many think!