I use the one I am currently developing, I used to have the Intellidose and found it OK but thought it could do more, especially for the money.
I used to make electronic devices and code so when it eventually died I decided that making one myself would not be too hard (haha!)
That was 18 months and many thousands of pounds ago...
I now have a working and reliable device which is capable of operating loads of individually addressable pumps (up to something like 80-90), as well as firstname.lastname@example.orgA outputs for controlling relays which in turn could turn your lights on and off, or a humidifier, or a dehumidifier, or a fan, or a heater etc There is still some coding to do in this area but the hardware is there and is tested.
It stores a year of data and can display it on a built in 7 inch touchscreen. Currently it records TDS, PH, nutrient temp, air temp, air humidity and there are plans for the future to include options for CO2, DO, tank solution depth, nutrient bucket depth (or at least warnings on low level) I also have future plans to allow the user to control the doser over the Ethernet with a tablet. If I can find someone who knows how to do secure internet routing I want to expand the tablet idea so you can control your room from anywhere in the world from your smartphone.
Where most devices measure PH to 0.1/0.2 mine measures to 0.001/0.002. I am able to hold my PH in a range smaller than most devices can measure, between 5.65 and 5.675 for example.
I have decided to call it the Microdoser as it can micro dose, it also has a microcomputer in it which will enable it to analyse your tank more than the currently available devices, so it could for example see that your plants had stopped taking up food and if that is in combination with a rise in PH warn the user about root rot, or maybe overfeeding.