BrainWave Generator is a Windows shareware app (30 day trial after which you pay $40) that plays specific sound frequencies to each of your ears, which will "take you to the state of mind you want." At least, that's what the BrainWave Generator web site says. Among the laundry list of possible uses claimed by the BrainWave Generator are:

* Relaxation and meditation by entraining your brain into desired states
* Enhancement of learning capabilities (super learning)
* Sleep induction (for treating insomnia or just for falling asleep quicker)
* Focusing attention and enhancing awareness
* Alleviation of headaches and migraines, as well as other pain
* Preparation for stressful situations
* Self hypnosis and/or subliminal programming

You can also save the audio output from the BrainWave Generator and take it with you on your iPod.