extremely useful. Let's say you're out of town on a business trip for the weekend... and your temperature starts going haywire. First, your heaters are connected to the DC8 which controls them, so the temp starts climbing the heaters get turned off... continues climbing, and you get sent an e-mail telling you that something is wrong, and that your current temperature is higher than usual. Well it still climbs so your lighting turns off. Same sort of thing with your PH, it suddenly starts falling, your AC3 will start dosing kalk from your kalk reactor, or shut off your Calcium reactor.
With their included software, you can view live stank stats from anywhere in the world.... even control the equipment remotely. You can seriously set your AC3 to a certain longitude and latitude, and have it mimic that area's actually seasonal temperatures and solar/lunar cycles!
They're amazing.... I wish I had one.