Not really anything about hypnosis but certainly verging into areas of outright mind control, this article in the Io9 website is a bit light but still at least interesting reading and maybe a little thought-provoking. The article lists ten different ways electro-magnetic fields can affect brain functionality, usually to the detriment of the person affected. These ways are:
10. Shred its DNA
9. Stimulate its Growth
8. Train you off food and water
7. Make you spin in circles
6. Pacify you completely
5. Alter your morality
4. Take out your power of speech but leave your ability to sing
3. Induce panic, disorientation, and deep fear
2. Cause Seizures and Death
1. Make you see ghosts
Sound far-fetched? In reality, research is already underway in ways to make use of electro-magnetic fields (and similar energy projection methods) in combat or crowd control situations. There is already in use a high-frequency, high decibel sound projector that has been in use for crowd control situations in recent years. Not to mention the alleged secret government experiments into similar mind controlling devices in the past.
Now can this be applied to hypnosis? Well, hypnosis is a complicated state but one that is definitely affected by the mental state of the subject. Could the brain be so stimulated through electro-magnetic fields that can induce a trance-like state that can be used to effect a hypnotic state? Given that several MRI studies have shown which parts of the brain are in operation during hypnosis (studies which show that the brain in sleep uses different areas, demonstrating that hypnosis is not a form of sleep) these areas could be targeted for stimulation in induce that effect.
Of course, the article here needs to be treated with a certain level of skepticism, but the idea is worth keeping in mind.