Aha, I found the snake in the grass. It's not a very big one, but still. You need to replace a kind of chips every month, they cost 21 euro for a package for 3 months or 84 euro for one year.
I found the user guide: http://www.seneye.com/media/documentation/User_Guide_UK.pdf
They have special prices and stuff for people doing research. Are we researchers?
In the manual they say something about an upgrade coming up, with nitrite, nitrate, hardness and chloride testing... All existing devices will be upgradable.
There's also a small text that implies they're opening their API.
I think we should contact them and try to get the whole package (with extra tests and API) and become testers for them. Then we can design our own graphics page :-D