Apparently, it's better for your plants to water them in the evening, so the water doesn't evaporate quickly and they can soak up as much of it as they want. Unfortunately, that means you need to garden in the dark, which is a pain.
This garden hose nozzle has a light on it, letting you see exactly where you're spraying. It works well for nighttime gardening as well as nighttime hose fights, where you'll have an obvious advantage. Especially if you're the only one with a hose.