Does this method work for anyone? It seems to always return 3700 for me. Just wondering if there is any way to detect the battery state without a voltage divider/analog pin combo.
Works fine here 
used a voltage divider and analog pin though 
http://robertjacobs.eu/2011/02/03/voltage-dividing-reading-battery-voltage/
Oh, I was just using the static Battery.ReadVoltage without initializing it with an analog pin. I was hoping there was enough circuitry in the Fez to read it without needing the resistors and analog pin but I guess not.
It is, but you can only use it for a certain voltage. Since usbizi runs on 3,3v you can read maximum 3,3v on the analog pins.
So probably your battery is around 7 volts, which you cannot directly read with the analog pin. Therefor you would need the voltage divider 