I may try one of those some day, I have grown fond of my Battery tender though, it may not be waterproof, but they do sell a waterproof one, I like how well ventilated mine is, the C-Teks look like they'd have trouble dissipating the heat, at least given the way I constantly leave mine hooked up to the car.
Of course in my case I do still have a bit of a parasitic drain that I have been too lazy to track down.
I am not really convinced the desulphation phase really does much good, if a lead acid battery is let run low for so long to the point a battery is failing from sulfation, you'd think the desulphation phase may give it a little more life, but I think that would be a short additional life, at that point it is most likely better to buy a new battery.
That C-Tek does look cooler than mine though.
Found a good read on sulfation.
Sulfation and How to Prevent it - Battery University
"Several companies offer anti-sulfation devices that apply pulses to the battery terminals to prevent and reverse sulfation. Such technologies tend to lower sulfation on a healthy battery but they cannot effectively reverse the condition once present. Manufacturers offering these devices take the “one size fits all” approach and the method is unscientific. A random service of pulsing or blindly applying an overcharge can harm the battery in promoting grid corrosion. Technologies are being developed that measure the level of sulfation and apply a calculated overcharge to dissolve the crystals. Chargers featuring this technique only apply de-sulfation if sulfation is present and only for the time needed."
If you read that it seems sulfation mainly comes from a batter not maintaining a proper charge, so if a batter is properly maintained (being deprived of a full charge) it seems desulfation would not really be necessary.