I've heard that your sleeping mind does better with non-obvious messages. Like messages you can barely hear, or need to decode. I think the only way the signal will enter your dream is if it is interpreted by your sleeping mind, and integrated into the dream. Similar to how you described the Nova Dreamer's lights being integrated into the dreamscape. That is sort of the point.

The reason the nova dreamer works (for some people) is that it shows you a signal in your dream, that reminds you to question whether you are dreaming. It doesn't just flat out tell you you are dreaming. The important part of that equation, is you noticing the signal on your own, and remembering to do a reality check. That is where your logical mind wakes up. When you interpret the sign, remember what it means, and remember your intention to RC. It needs to come from yourself and your own curiosity.

But I've never tried. I've just known people who have.