Do you eat enough fruits and vegetables? Of course you don't. And to punish you for this lack of nutritional awareness, Yale researchers have developed a laser system that can measure your intake (or lack thereof) of healthy foods right through your skin.
The whole reason for eating things (besides tastiness, of course) is to provide your body with energy and raw materials to keep it functioning at peak efficiency or whatever your existence passes as. This means that the building blocks of the stuff that you cram down your gullet eventually show up in your blood and in your skin as what are called biomarkers, and testing one or the other can reveal what kind of nutrition you've been getting recently. Problem is, as vampires and pirhanas will tell you, getting people to give up blood and skin on a regular basis for testing (or anything else) isn't easy, which is where the lasers come in.
One of the biomarkers for fruits and veggies are called skin carotenoids, and Yale School of Public Health scientists have figured out a way to measure them directly using lasers. All you have to do is shine one of these lasers on your skin for 30 seconds, while a fiber optic probe looks for the signatures of carotenoids as the molecules react to being excited by light from the laser. After 30 more seconds of analysis, a computer spits out results that are apparently "highly accurate," showing how much in the way of fruits and vegetables the subject has been eating recently.
Being able to test for nutrition non-invasively and in such a short amount of time opens up lots of new possibilities for making sure that people, especially kids, are eating what they should to stay healthy. There's a lot of refinement to do on the hardware (which is rather bulky at the moment), and a lot of calibration will also be necessary to figure out how long skin carotenoids stick around after you eat and to what extent skin pigmentation influences the results. We're excited, though, because non-invasive sensing techniques have the potential to make it fast and easy to keep track of your personal health, and we're getting close to being able to just wave a tricorder at someone to figure out why they're not feeling well: "I'm a doctor, not a botanist, but according to these readings you're not eating enough vegetables. Go replicate some glasht and contact me in the morning."