Behold the Plant Smart Digital Plant Care Sensor
This device will tell you if your yard is sunny (in case you can't figure that out yourself) and if you need to water (here's a hint, if it hasn't rained and you haven't watered then you need to). Their website also mentions measuring soil fertility, however does not explain how or what it measures. Knowing what I know about agronomy (excellent soil science professor to thank for that) I'm not really sure how it's possible for a sensor to measure soil fertility, it's just not how soil testing works.
When Black and Decker first released this product it was called the "EasyBloom" and has since been renamed and rebranded. Half of me wonders if there were some crazy lawsuits brought by people who's gardens didn't miraculously bloom easily with the use of this product. But what I love best about their website is the assertion that, "the EasyBloom Plant Sensor helps any ailing plant AND gets you the garden of your dreams." Wow, I guess I've been doing it wrong this whole time. And really, could it get less realistic looking, as if this thing is going to blend in against your plants. That is, unless you have fake plants (you are out there and I know who you are!).