This DIY blink detector can be made in less than 10 minutes for under $10.
A borescope is mounted on a goggle to the side of one eye. Software interprets the camera’s video image to identify two (maybe three) eye gestures. The user could use a scanning ‘keyboard’ to blink out a message. Alternatively, she could blink Morse code.
Instructional video: https://www.youtube.com/watch?v=C95J9l0416I&feature=youtu.be
The borescope is mounted on a goggle so the camera does not move when the head moves, thus making the design a lot more robust than one that uses a web cam (see https://abilityspectrum.wordpress.com/2015/05/18/blink-is-bliss/)
The software is made with Processing and has been tested on OSX. Work is progressing to make the software cross-platform.
We also intend to add functions such as email and texting.
https://github.com/AbilitySpectrum/blink_based_aural_scanning_keyboard_with_Morse_code_option
Ability Spectrum 
I’m interested in trying this technology. Do you offer detail design instructions?
There is almost no finesse to this. The borescope and goggle can be purchased on-line. The software is hosted on github. It runs on the Processing platform and has been tested on OSX.
When the software runs, it shows the video image. You need to adjust the borescope so it aims at the eye. I use Sugru for putty. It allows adjustments for a few minutes. It then hardens overnight.
Initialization procedure is shown here: https://www.youtube.com/watch?v=1–6nZVQz3c and https://www.youtube.com/watch?v=C95J9l0416I
Please private message me if you need more details.
It appears the boroscope is a bit more than $10.
A good borescope costs more. But I’ve had success with inexpensive ones available on aliexpress. Search “5.5mm 7mm borescope”. Be sure to buy one with a side mirror.
Very nice videos of the eye blink detection and very good work in general. Thank you for sharing.