Well it's not entirely true, you can hook up solenoids to control the flow at different times to different misters. But the question gets to be how much work and how much trouble shooting do you need to do to pull that off and maybe it will just be better for you to buy 2 misting systems 1 for your chameleons and 1 for your dart frogs. I would say its just easier and way more simply to buy 2 starter systems.
Also, its worth nothing that extra misting will not be a problem for dart frogs if their habitat is set up to handle it. Chameleons and dart frogs actually live in similar tropical environments the difference is dart frogs have great resistance to low air flow and chameleons do not. Some people only mist their chameleons twice a day, some people mist their dart frogs 5 times a day. With proper thinking and design you could easily get one misting schedule to work for both animals.
There's great info here, worth reading again and repeating some bits with emphasis:
1) In my experience, just getting another pump and timer is great, if you have two substantially different watering-schedule needs. Like if you had a collection of orchids (or animals...) with 2 basic watering regimes, e.g., 3x every single day is just fine, vs 1x/day, only twice a week is plenty, and more would be too much. I have two pumps, each sucking off its own reservoir (a 10-g aquarium) and with its own timer (and quite different watering schedule) and I absolutely love it. (Both timers are set to automatically provide not-quite-enough water for the different plants and animals they service. That way, I still have to get in there every couple of days to have a look around and, if things look thirsty, I do a little hand-watering. And one of those aquaria needs topping off a lot more often
than the other one.)
2) However, if you don't really have substantially different watering-schedule needs - then yes, one pump and timer CAN work. Or you can screw it up! Ha ha. I think that since you already have these animals, and their cages are already designed, built, planted, occupied etc etc - it would be safest, fastest and cheapest to just buy that second system.
Another thing to consider - if I've got this right
, misting for the frogs is about keeping up ambient humidity and skin moisture. Whereas misting for chams is about getting them drinking; in my experience squamates can say "no thanks" to many chances to drink, but then when they do
want a drink they can drink for minutes on end. "Wow, like, forever!
" Ha ha. So I would think that the frogs would be fine with frequent short bursts, but the chams would need the water to run for longer, but maybe less often. Anyway, I have never actually kept a single one of either, so feel pretty clueless on the subject. Just a reader and guesser.