I, along with another member of my household, suffer severe motion sickness. So, of course, I bought a boat. Drugs can combat this condition, but come with a host of side effects, ranging from drowsiness to psychosis. "You've got that look in your eye again, skipper..."
While researching other remedies, I came upon this NASA report on using stroboscopic vision to reduce motion sickness. The report indicates that the stroboscopic effect can be produced through lighting or LCD shutter glasses. I happened to have a few pair of LCD glasses from a previous project, so I figured I'd give this a try. They're not the most fashionable pair of goggles you can imagine, but if this works, there's no reason an attractive version couldn't be made.
The paper states that flash rates of 4 or 8 Hz with "short dwell times" were found to be effective. Driving LCD glasses is relatively easy: you just apply an AC waveform to activate (darken) the shutter(s), taking care to eliminate any DC bias which can damage the elements. For something this simple, there's no need for an actual LCD driver, bit-banged IO on a tiny microcontroller will work just as well. You can probably find smaller or cheaper solutions, but I have a stash of PIC12LF1571's around which will do nicely for now. Powered from a coin cell or cylindrical LiMnO2 cell, the battery lifetime should be very good.
EDIT: I just found that these are already a thing! But, at $131/pair, there's room for a hacker's version that should cost a small fraction of this.
So, the next step is to hack together some code that will flash the glasses at 4 or 8 Hz and around a 90% duty cycle (10% clear). Then see how it works. A ride in the back of the car will tell me very quickly if it works.