It's not an LVC, but if you mount it where you can see it, this might work well:
http://www.dealextreme.com/p/digital...c-models-10787
I'm buying a couple to use in case I run my lipos in a car without a cutoff.
They also have a 3s buzzer/alarm, but they don't seem to have any 2s or 4s versions.
http://www.dealextreme.com/p/11-1v-b...licopter-35609
Brijar