If Plants Could Talk: The water-me vase...

From designer David Sweeney on Yanko Design and through Gizmodo, the Water Me When I Tilt vase (which needs a new name) tilts down to horizontal when the water level is low., but sits at a 30-degree angle or so when sufficiently hydrated. Personally, I can't keep myself disciplined to water my plants, so a flagging/cuing/begging system like this could really make a difference. (My plant graveyard is getting full of those poor neglected and/or overwatered souls.)

There's also something about the tilting action that's more immediate or urgent than a blinking light or a beeping sound - it's a real part of your environment, a physical entity, not just a signal. Not to mention, of course, a neat conversation piece that's holding your not-dead plant!