As the title, a CBM that would automatically inject a drug into your system when it detects that the levels of whatever drug you’ve loaded it with are low in your body.
Alternately an activated CBM (would be a free action) to inject you with whatever drug you’ve previously loaded it with.
Useful for addicts as the initial one, or possibly to keep you good and caffeinated. The second one would apply to more situational drugs. You’d be able to load them, and perhaps it would take longer than just taking the drugs, but you’d be able to get them instantly later.
I see no use in that. Most of pills and reagents are volumeless, you can carry tons of them. There is no point of using CBM to get some drug instantly instead of spending 2.5 turns (250), because even if you happened to be in critical situation and need to use some drug RIGHT NOW - you’d better use adrenaline pump and proper pill thereafter.
I wouldn’t make it into a CBM but a custom built programmable wearable injector that could take a variety of different drugs and inject them every x hours could be useful.