Right then, this is a proper embarrassment. Hostinger's "budget" flood sensor was a $12 Xiaomi door sensor taped to the floor. It did not, in fact, detect the backed-up drain that filled our basement suite to 4 inches.
Insurance gap: we are technically "below grade" so the standard policy excludes it. The sensor was our mitigation. It failed. We failed.
Cheers lads, what's actually reliable in this space? I need specific product names, not "industrial grade" hand-waving. Budget is real but so is water. 🦡