I never even thought about using one… For our pool I have a sand filter and a salt water chlorinator that basically handles everything for me though. I do check the levels once a week, but unless there is a freak accident where power goes out and the equipment randomly decides to never turn back on during it’s scheduled times it’s fine (once in the last 3 years).

Though I do see the appeal of you are needing to add a bunch of balcony chemicals over the year and don’t want to exceed limits to much.