I just bought a Seneye from the UK. Should be here sometime in the next week or 2. Figured it would be a fun gadget to play with. My 6 month old "cheap" LED unit blew out 2 days ago and I had to order a new LED Fixture (I modified the old one to split the blue and whites on timers, so no warranty).
I was hoping the Seneye would give me some idea of my lighting parameters. The subscription service isnt' required, its a pay as you go, while the slides you replace only last about 30 days each ($10 a piece), if you don't replace it you just won't get free ammonia and pH readings. All other parameters, such as Temp, Water Level, PAR, LUX and Kelvin (along with the spectrum analyser) all function without the slide.
The company has also stated they are working on adding additional parameters. They have named Nitrites, Nitrates, Chlorine, Carbonate an General Hardness to the additions of the . Best part is that they will be useable by existing Seneye users for no additional charge.
I'll let you know how it works for me. I'll be running my API tests along side it to see how accurate it is throughout the month.