I'm not exactly a chemist, but It sounds like this device just electrolyzes a saturated salt solution to produce a sodium hypochlorite solution, AKA "bleach". Ref:
http://chem.lapeer.org/Chem2Docs/chlorine.html
I guess the advantage is that salt and lithium batteries have a longer shelf life than liquid bleach or tablets.

That brings up a question - On the ETS site it seems to say that only MIOX and Micropur MP1 tablets will reliably kill *everything* including Cryptosporidium. For some reason, I was under the impression that bleach is 100% effective also?