UV rays are present all year round, even on cloudy days, and now you’re more sensitive to them, it makes sense to stay alert. A smartphone app makes it easy to keep an eye on your local UV index forecast. HappySun (free, itunes. com) also measures the amount of UV rays your body absorbs and lets you know when it’s time to move out of the sun. It can also give you sunscreen advice based on your location and your skin type.