Robust low battery cutoff
OK, this is a fun one to noodle around with. Assuming that the R.C. pin on the regulator is pretty high input impedance, this might be one way to do it if you get a kick out of building from basic components:







simulate this circuit &ndash; Schematic created using CircuitLab

This circuit consumes about 20 uA. The turn-off threshold is controlled by choosing the R1/R2 voltage divider, which turns off Q1 when the Q1 base voltage falls below the base-emitter diode drop. This, in turn, happens when the battery voltage falls below some value (11.4 V, in this case). The threshold is a bit sensitive to the R1/R2 values, so you might either want to add a small series trimming pot, or at least another smaller value in series with one of them to fine tune the threshold. 

With these values, the threshold is around 11.4 Volts. Simulation output is below, with voltage on the vertical axis. The battery voltage swept from 11 to 12 volts (blue trace) and the output (orange trace) taken from the collector of Q2. You might want to add an aggressive low-pass RC filter on the output. Sorry for the tiny fonts on the graph....don't know if I can change that on CircuitLab. You can see a reasonably sharp jump in voltage output as the battery voltage crosses 11.4 V.

The turn-off threshold will have some non-trivial temperature sensitivity, but it might just be tolerable for this application.