i was thinking of something like a pressure regulator. might take a bit of fiddling but you could conceivably have a grow where you really just do absolutely nothing for the most part. but yeah if you're going to be spending that much time in with the plants anyway there's really no point. i could see it being useful for either small, low maintenance home grows (+stealthier than a reservoir) or a bigger commercial grow.
not to hijack the thread, but do you do the full biotabs regimen (all the additives) or just the tabs themselves?