The only way he can interact with hardware is by... blinking. And were gonna do this.
Therefore, I was wondering: does anyone have a viable blink sensor on the cheap? It has to be fast enough to detect deliberate blinks
In your shoes I would start with a webcam and the trial version of RoboRealm or other vision SW. Rather than trying to physically detect the eyelids moving, you should be able to see them moving. Or if you struggle with the eyelids, roborealm can probably be programmed to see the pupils (eyes open) and not see the pupils (eyes closed).
www.roborealm.comWith vision SW, you can potentially improve performance and add functionality even remotely by just updating the algo. Maybe a look to the left or right can be added to increase the number of inputs possible.
I'm sure if you explain to the roborealm community what you are trying to accomplish, you'll have people lining up to help you.
I just checked the roborealm page. There is a module there already to get you started:
Machine Perception Toolbox
The MPT is a cross-platform collection of libraries for real-time perception primitives, including face detection, eye detection, blink detection, color tracking. Future versions will also include expression recognition, predictive color tracking, and tracking based on multisensor fusion.
Good luck!