Workouts++ is a new app for your Apple Watch from David Smith. It allows you to customize your workouts and view them in new ways on your iPhone. I am a long distance runner so I won't be writing about how Workouts++ works with a bicycle, on a rowboat, or in a Yoga class. Instead I can tell you how Workouts++ has helped me target my training for this year's Boston Marathon. Workouts++ is three apps in one. The first is a factory for building workouts on iPhone. The second is a monitor for tracking workouts on Apple Watch. And the third is a database for comparing workouts on the iPhone. Workouts++ starts on the iPhone. Pick an activity &emdash; indoors or out &emdash; and Workouts++ lets you select what information you see on your Apple Watch while you workout. Up to six different metrics can be shown on Apple Watch at a given time, with options for size, style, and color. You can't switch metrics mid-workout, but you can name and save as many customized workout as you like. I named my first watch face 'Marathon,' and chose metrics I want to see while running on Patriots Day. Speed is displayed above distance and duration, because I am targeting a three hour marathon and need a constant speed of 8.8 MPH to meet my goal. Workouts++ lets me display my speed in red if I slow down or go to fast. This alert can be further enhanced with haptic feedback. After my run is complete, Workouts++ logs my workout in its database. Workouts can be filtered by activity and duration, and sorted by date, duration, distance, or active calories. This makes comparing runs of the same distance easy, even for workouts performed outside the Workouts++ app. David promises swimming workouts and location mapping in a future release, but I would appreciate improved performance from Workouts++. Unlike the built-in workouts app, Workouts++ takes a few seconds to calculate my speed each time I raise my wrist while running. This two second delay often leads to false alerts and unnecessary haptic feedback during the race. I want Workouts++ to succeed because it makes important metrics easier to target, but as an app it is useless if I can't trust what it displays My guess is that David is doing the best he can with the design constraints of Apple Watch. The metrics Workouts++ presents at the end of each workout are accurate. but Apple is restricting what kind of calculations can be performed while Workouts++ is in the background. I hope Apple works with David to give Workouts++ better real-time performance in time for my race, but in the meantime I will still be using Workouts++ for training. The open app ecosystem is what makes the promise of Apple Watch so great, and fitness apps like Workouts++ are playing to the platform's sweetspot.