Cool link. It would probably be a really cool project to build but using it in real life would be a total pain in the ass since you have to recalibrate it every time you use it, "The two other potentiometers are used for calibrating the pH meter before each use using known pH solutions."
Plus it costs about 100 euros, "You now have a tiny high-accuracy pH-meter that costs less than 100 euros." For that amount you could buy a good, self calibrating pH meter.
All that being said it does look like a fun project for someone into electronics but it's just not very practicable for everyday use. The reason it's so good for classrooms is you WANT your students to learn how to calibrate devices...