Aquarium Heater Control - What Do You Think?

Interesting idea.

You could always test it by turning the heater settings up slightly. The fish shouldn't come to harm as the temp won't be higher than usual for long if the controller works. They have to cope with spells of warmer water during a heatwave and this test should be no different from that.

Seems like it'd work, but strikes me as feeding your paranoia and will likely prove unnecessary.
Unless you're a very unlucky person and then you might want to consider this setup doubled up with 4 heaters. 

My shrimpery got killed by a malfunctioning heater but I'm not techno savvy...come on you know some of you guys love tinkering with mechanical stuff 

@Evolution Stu - I wholeheartedly agree with your logic.

Stu,
Your method will definitely work, and its a good idea to have the second level of control, its normal practice in boilers and ovens. One control does the work clicking on and off and the other just stays closed until its really needed. Neither guard against a short circuit welding the contacts closed but this will almost certainly take the fuse out so its still safe.
I use a central heating controller for my tank a - field return so it was free but I use it in the 'normal' way with the heater thermostat set just above the controller temperature.
I do it this way because a dedicated temperature controller generally controls temperature better than the mechanical controls on the heaters and I can set the tank temperature on the display rather than the small dial on the heater. It also has a separate sensor is so its not affected by the heater itself.
A large number of our controls can now be controlled over the internet so I could see the tank temperature on my phone (I don't because that of course is weird) We even have central heating controls that could run 12 tanks (rooms) at different temperatures so if your MTS develops into a fish room I can suggest a good solution