Hi,
this is a very interesting question and I feel like I might be able to give you some answers:
1. Biofeedback devices
Professional grade EEG Neurofeedback: go and google Pocket Neurobics or brain-trainer - there are many evidences that EEG Neurofeedback can optimise your brain patterns which can dramatically affect cognition. There are several links for further reading and also a few anedcdotal evidences:
http://www.longecity...-neurofeedback/
http://www.longecity...and-discussion/
http://forum.bulletp...sync#entry93746 (read post #4)
You can get Q-WIZ + ecap + BioExplorer (software to run it on) + assessment for about $2200. The training protocols mostly used by members of longecity are either TAG Sync (stands for theta-alpha-gamma synchrony, just google) or TLC7 from brain-trainer.
You can also go a more expensive but perhaps more straightforward way with Neuroptimal neurofeedback from Zengar.
Consumer grade EEG: there are several of them, notable mentions being EMOTIV, Muse or NeuroSky. Personally, I would wait for EMOTIV Insight, which will be released in the beginning of 2015. It has 5 dry electrodes and gets connected to your smartphone.
nir/pir-HEG Focus training - stand for near/passive infrared hematoencephalography (or something similar ) - basically trains you to increase the bloodflow to your brain, or specifically to prefrontal cortex. Which is great for focus. You need an amplifier such as Q-WIZ (or even a cheaper one), altogether all the setup is for about $1000. I use it ans have very positive result after 4 days of use. Further reading:
http://forum.bulletp...and-heg/?hl=heg
HRV training: heart rate variability is linked to cognitive performance. Have a look at the Inner Balance device. Basically, you pay about $120 for just a sensor which might seem a lot, but it can be very beneficial.
2. Electrical stimulation devices
tDCS and/or CES: first stand for trancranial direct current stimulation. You just place electrodes on your head and let some (mili)amps flow into your brain. Backed by a lot of research. Runs for about $200-300
http://www.foc.us/
http://thebrainstimulator.net/
3. Light stimulation
Check out Lostfalco's thread about the TULIP stack. You basically place red led diods on your scalp for several seconds which arguably promotes mitochondrial metabolism and let them work more efficiently - improves cognition. Very experimental but worth checking out. You can get one for as little as $30. Mine is for $200.
4. Others
Exercise - actually dumbbells and barbells can help you improve your cognitive abilities by a big margin. Regular exercise dramatically raises BDNF production in the brain (that was found in mice).
Dual-n-back - not really a device per se but worth checking out
Meditation - also, there is a link between cognitive performance and mindfulness levels. Regular meditation helps you block out distractions which can lead to better focus - performance.
Mozart effect - and other sound entrainment. Do a google search.
For some interesting reading, check out the book Smarter from Dan Hurley for tDCS, n-back and some more or A symphony in the brain for some very light reading about Neurofeedback.
I'm personally using or I'm going to use most of those device in my intelligence improvement project. Check out my thread http://www.longecity...emax-lllt-tdcs/ or my blog http://www.effectivebrain.com/ for more info.
Edited by Candidatus, 31 October 2014 - 05:29 AM.