I use rheostats on my BP tubs, and they are pretty foolproof; they do not allow more power than I set them at.
Now, I plan on switching to my Helix thermostat once it is done being used for my incubator in a few months.. It is an awesome thermostat and worth every penny I spent on it. I do not feel that it needs a backup, but everyone is different and responsible for their own actions I guess. I had a power outage while running it, and it was "smart" enough to remember its setting before the outage, and that gives me confidence.