Couples alarm clock: rings that you put on your finger that vibrate to wake you up so that it doesn't wake up your significant other. --- but it would vibrate the bed. I can always hear the other person's cell phone
One pot, two lives; a planter and a fishtank in one to promote a beautiful example of simbiotic living. While the fish's waste provides nutrients for the plant, the plant filters the water that it is fed to provide clean water for the fish.