This is one way the quantified self goes mainstream: Automakers are testing a brain-wave-sensing system that sounds an alarm when it detects sleepiness. A lot of people look at an emerging trend, and do a linear extrapolation. And certainly, there are interesting businesses along the direct trend line of the quantified self - fitbit, withings, Fitness Keeper (in which OATV is an investor), and even monitoring of clinical indicators like glucose levels. But there are also lots and lots of investments along the broader front of which the obvious applications are simply harbingers.
This story about the potential use of EEG-monitoring headrests in cars to detect drowsiness (and might we suspect drunkenness?) is one good example. It seems to me that there will be applications in security (biometrics), in control systems (think how Kinect has already been used for everything from a motion controller to a monitor for the progress of neurological disorders), and in passive affordances for the "internet of things" like the ones described in this article. (via @slashdot)