How do you tell if a half-used jar of tomato sauce in your fridge is still good? If you’re like us, you just open it up and take a deep whiff. But this little gadget could take the guessing (and unpleasant sniffing) out of the equation! We just read about it in the NYTimes House & Home section: Daysago. Stick it on your food jar or box or whatever (it has a suction cup on the back) and press the button to activate the days-counter. Presto! Click here to buy, two for $10, and they come in four different colors, too.