Yeah, I know 1 degree is tight. I plan to tape the sensor to the outside of my carboy and insulate it from the air in the fridge. Given this setup, the temperature of the beer will change pretty slowly, so I don't expect to be cycling the compressor too much. If so, I can increase the differential. I would at least like to have the option to go less than a degree differential if possible.
I take it there isn't much out there that can do less than a degree differential. Fermentation temperature +/- 0.5F sounds pretty good, so I guess I wouldn't complain if I couldn't find anything.