I live in FL and have similar concerns when on vacation. What I do is have the pump suction set only to the main drain (no skimmer) when I go out. Alternatively, you could get an autofill device like this one: Rola-Chem-M-3000-Rola-chem-Pool-Sentry Of course you run the risk of flooding the backyard if the thing were to fail and get stuck "on".

I can't find any low water shutoff switches specially designed for pools, maybe someone else has seen one.