WaterMinder ($1.99)

We all know that drinking water is good for us, but it's still easy to fall short of the recommended eight glasses a day. WaterMinder offers a visual representation of how much water you've had to drink, displaying your progress as a percentage of your daily goal, along with the number of ounces you still need to guzzle. Get reminders when it's time to pour yourself a cup, and log your intake right from your wrist. Other features include the ability to create custom sizes (perfect for those oddly sized water bottles!) and a graph displaying your water intake over the past two weeks.