That is interesting, but seems a bit overboard. Wouldn't those be expensive or hard to clean? You can get addition funnels with threaded teflon drip valves and they are a hell of a lot easier to clean. Even regular press. equ. addition funnels have good adjustable rates. Personally I wouldn't like having to reorder equipment for purposes like that. I just see repeated orders of things to be diverted for illegal work as a liability. Even if they are cheap and disposable, it would add to the incriminating trash pile. I would prefer to just rinse a glass funnel out with some solvent and pop it into the ultrasonic cleaner. Bam, evidence gone in five minutes.
Just personal preference. It is cool though, because those things have a killer drip adjustment. If I had the means to acquire them without suspicion or ebing looked upon as a junkie and had an incinerator I'd consider it.
What are those bags made of that you speak of? I just don't see them being able to hold some of the oxidising mixtures, solvents, methylating agents, etc, that one might want to introduce by drip addition.
I guess another great thing is that some IV bags hold several liters of fluid. In that case it makes for a cheap addition funnel compared to buying a 4l funnel and trying to transport/store it, making a great addition to a porto-lab/disposa-lab.