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.
http://www.seneye.com/store/accessories/seneyeplus.html
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?
http://www.seneye.com/research
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