I was fooling around with This idea back in 2012 but didn’t know about eagle then and it’s still a space hog unless we can find a smaller quad opamp but it would give up to 4 - step accuracy.
Edit- Post 23 of that thread has a hand drawn layout for reference. It uses a sot-89 voltage regulator for chip power and a sequence of voltage dividers for the comparators.
This is the chip I bought for this.
Here is the circuit mentioned in the linked post. 
The resistor values can be adjusted for different voltage steps and I think I did those calculations already.