I got up at 3 AM to use the bathroom and stubbed my toe on the doorframe so hard I saw stars. The next day I ordered a pack of motion sensor lights. They cost $15 and they have been, dollar for dollar, the best home improvement purchase I have ever made.

Motion sensor lights are small LED strips or pucks that stick anywhere and light up automatically when they detect movement in the dark. Here is why they belong in every home.

Where to put them

The obvious spots: bathroom, hallway, stairs. But also under the kitchen cabinets (midnight water run), inside closets, in the garage, and along the baseboard path from your bedroom to the bathroom. I put one under my bed frame so when I swing my legs out at night, the floor lights up before my feet hit the ground.

The specs that matter

Look for lights with a passive infrared (PIR) sensor, not just a light sensor. PIR detects body heat, so the light triggers when a warm body enters its field, not when the ambient light changes. A detection range of 10-15 feet and a wide angle (120 degrees) means you do not have to wave your arms to activate it.

Rechargeable battery models are the most convenient — charge them via USB every few weeks, stick them anywhere with the included adhesive magnets. Some take AA batteries, which is fine if you use rechargeables. Wired plug-in models are best for permanent installations but limit placement.

The specific model I recommend

The AMIR motion sensor LED strip (or any of the dozens of clones — they are all basically the same) comes in a pack of three for around $15. Each strip is about 10 inches long, has a PIR sensor in the middle, charges via micro USB, and lasts about two weeks on a charge with moderate use. The light is warm white, not that harsh blue-white that makes a bathroom feel like an operating room at 3 AM.