You can get SOME cardboard apps to work without the controller, IF you turn off NFC, problem is in some cases you then have no way to select things, although some apps will autorun, or you can stare and select. JauntVR is an example of a stare to select app that works in Daydream with NFC off, with an iPhone for example. Of course we no longer need to do this as the JauntVR developer worked with Google and it is now officially supported and available in the Google store. BUT I had it way early.
