Ha! You'll be lucky. The first thing you'd need to understand is the various ions in solution at neutral pH when calcium is in equilibrium with various concentrations of CO2 and at various pH levels near neutral, which is a highly complex system. Then you'd have to work out why and how a magnetic field would influence those ions to prevent crystal growth and precipitation.
I wouldn't go as far as to say these devices don't work; they may, but it's certainly not obvious why they should, and attempts to prove they work by experiment don't seem very successful, so the science is going to be difficult, even assuming there is any.