That i could see but not everyone who is stoned is typing on their phone all the time. Article makes it sound like it can do this automatically unobstructivly.

Seems far easier to detect the sound of a lighter, crunchers hitting eachother and detecting sentence like “i am going outside to smoke my joint” combined with daily/weekly patterns in time.

Thanks to this i did find a great nerdy app to play around with my phones electromagnetic field sensor though.