I picked up one of these little analog VOC sensors from RS the other day and wired it into a voltage divider circuit.
It's a potentially useful way of detecting electrolyte leakage from the battery, especially during charging. Generally, if a cell leaks electrolyte during charge, things are about to go bad shortly, but if this can detect it, and cut power, you might just save your house.
I used acetone on a tissue to get it to go off, but it seems to be very sensitive - took ages to come back down to a fairly steady baseline of 1.9 V (divided from a 4 V supply). Acetone is really volatile so it goes crazy, but the solvent in Sikaflex (mainly toluene) did the same, it just took a little longer.