The NovaDreamer is a device sometimes used to aid in the induction of lucid dreams. It consists of a mask worn over the eyes while sleeping. When the NovaDreamer detects eye movements that signify dreaming, it flashes lights in order to remind the person that they are dreaming.
Since stimuli such as flashing lights are often disguised in dreams (as, for example, car headlights or flickering light fixtures), having lucid dreams still takes mental practice even with the NovaDreamer. Therefore, the NovaDreamer is not a magic device that will give you lucid dreams - it is simply an aid to lucid dreaming.
It is marketed by The Lucidity Institute, but is distributed independently.
The NovaDreamer has been discontinued and is fairly hard to find. However, the DreamMaker is a similar lucid dream induction device. This device is also a mask that utilizes lights and sounds to signal the dreammer that he/she is dreaming.