I've had some overnight, unattended, cooks. Some went well, some didn't. The one that went the worst was this past winter when I woke up to see freezing rain bouncing off the cooker. The dome temperature was half of what it should have been.
That's nothing more than a lack of a proper plan and a dumb cook that didn't take weather into account.
I'd hesitate to rely on electronics. I deal with broken electronic on a daily basis (automotive), so the chances of finding them on my personal cooker will be slim.
I can't speak of the reliability of these devices, but I did watch an episode of Pitmasters where a gal lost her chances of winning because the electronic bells and whistles failed in the middle of the night.
For me, I'll rely on the knowledge I've gained by using my cooker and trusting that I know its capabilities and limitations.
That, and knowing my own personal capabilities and limitations. I am, after all, my own worst enemy.
Meat eater. Woodworker. PS3 Gamer. Home Theater Guy. Beer Drinker.
WSM 22.5 and random cooking stuff used to help form my shapely manly figure.