I had heard that many people get headaches when the humidity rises so I came up with the pseudoscientific idea to put together a sensor on an arduino that would log a snapshot of the time/date/temperature/humidity at the push of a button. I found an old Gucci eyeglasses case and everything fit inside perfectly. The patient was to pull out the GucciDuino when migraine began and turn it on for about 30 seconds to obtain measurements and then turn it off.
I used the SHT1x Humidity sensor, an SD shield by AdaFruit.com on top of the Freeduino (freetronics.com) and a 9V battery pack. I mashed together Lady Ada's Humiduino code http://tinyurl.com/3ux69xf, Jon Oxer's SHT_1x library, which you can find here: https://github.com/practicalarduino/SHT1x and I got help from friends at the NYC Resistor Hackerspace to guide me and further tweak it.
The data was inconclusive, partly because this was not real science and partly because the project was an excuse to solder. I love to solder. I hope to eventually use the data for something visually fun using Processing Language.