The kickstarter MindRider just started last month. MindRider has created a bike helmet that has an embedded EEG in order to read your brain waves as you ride.
The MindRider product also comes with an app that displays a map of your mental state at various points on your journey. MindRider calls this process creating a "psychogeographical" map of the city.
MindRider hopes that these maps will allow you to notice certain parts of your route that stress you out more so than others and that you may be able to avoid these stressful places. In the near future MindRider will likely combine community data to create psychogeographical maps of whole cities and will be able to identify with this group data rides that are enjoyable and peaceful and rides that are nerve-racking and hectic.
It seems likely that quantified selfers will soon have many opportunities to track not just their steps and heart rates, but also their brain patterns.