ACID vests are rarely used. Mostly because they only store a limited amount of chemicals, run on a battery, and only detect things cured by unga. Best use might be to inject peri if o2 goes beyond 25 in hopes to stop random punctured lungs.
What if they were used for drugs that didnt need a high dosage though? If it could detect broken splinted bones, it could inject an early found level 1-3 bonemend to fix. Maybe some other statuses and early chem findings could make it useful.
Alright the real idea though. Have it detect when a marine gets hugged and inject cyanide to try and stop the cap. You now traded your vest slot to potentially do more risky plays. Also if you were capped on frontlines you might have to get medivac’d in order to live again. Anti-para would technically work too. They would try to hug you til you died from the anti-para burn, or just a failed hug frontline.