heimdall-battery-sentinel

A battery power-level monitor for Home Assistant — the sentinel that hears the cells drain. It keeps the all-seeing watch of its name across every battery in the house, and cries out at the first honest sign of fading. It is written in Python and integrated with Home Assistant: battery levels tracked, thresholds watched, and the household told — through the channels the house already listens to — before the shore is seen. It exists because a battery warns exactly once, quietly, and a watchman whose single warning is missed has still failed his whole charge. This one does not intend to.

Cú Chulainn stood the lone watch for the whole province while it slept — one sentinel at the ford, cat-napping upright between challenges, because the province had agreed it needed only him. The household's battery watch is a smaller covenant of exactly that shape: a monitor for Home Assistant that hears the cells drain the way the watchman heard the grass grow, long before the shore was seen. Its namesake stands further north, the Norse watchman on the rainbow bridge who needs less sleep than a bird and whose horn is kept for one purpose — to be sounded early. The integration sounds its own quiet horn through the house's channels when a battery's power runs low, so that the dying happens in daylight, with witnesses. A round tower kept the same rule: one bell, rung before the shore was seen, not after. The moss grows up the tower on the north face, which is the side a watchman keeps to himself.