What kind of thermometer/hygrometer have you all used as a backup?
Are there any links to check the accuracy of both the temp and humidity?
Call me crazy, but I did not use a back-up for either. I did an empty 3 day test run with a wireless thermometer that we have here without knowing if the wireless therm was accurate. Both temps matched, which was good enough for me.
I did my part, ensuring that the outside temp was 70 or near 70, and relied on the built ins to do their job. After all, I did just fork over almost 200 bucks for this thing. It is my belief that those gauges had better be accurate!
My first hatch I started with 22 eggs. 11 were clears from day 3, one more was an early quitter. The remaining 10 made it to lockdown and hatched, all by relying on the built in gauges. I kept things a bit drier than the hygrometer suggested, not rushing to add water any time the gauge dipped below the recommended incubation humidity. I was careful to keep the humidity in the right range for lockdown and hatching, though.
I should also mention that my first hatch was literally my first ever hatch, both in the incubator and in an incubator in general. I followed the instructions, controlled what I could, and let the incubator do it's job.
I realize this may not be the case for all incubators, but it is what worked for me and this incubator.
I am super impressed with the incubator and its ease of use and clean-up afterwards. I highly recommend.