I took a look at a few running/fitness apps for my Series 2. From what I could tell, the only app today that uses the watch's GPS is from Pear Sports. I expect the Nike+ Running app will be soon updated consistent with the launch of the Nike+ Watch. I think the other major apps will soon have updates to use the watch's GPS. That was not a differentiator for me because I usually/always have my iPhone with me, but I would like the advantage of not having to carry it. I ultimately selected MapMyFitness / MapMyRun from Under Armour, but will discuss the others first. But first - what I did require: 1) Being able to use either my Apple Watch / iPhone (just referred to as AW from now on) or my Garmin Forerunner 920XT, which includes GPS and HR data. 2) Being able to use either input device either outside with a GPS signal, or inside without GPS - only HR. 3) Having a functional web site for analysis and documentation that includes workouts from both AW and Garmin Forerunner. Here's what I found: Pear Sports I got a trial subscription for a month. The regular subscription is around $30/year. The main thing it offers is guided workouts from their coaches. You can use it without their workouts, but in that mode, the functionality seemed limited compared to the other options. So I did not bother trying it inside or interfacing with my Forerunner. Strava Most expensive at $60/year for the Premium, which provides HR zones. Main claim to fame is the social networking aspect. Many running and cycling clubs and pro athletes participate, so there is both the social and motivational aspect. Works with the AW and the Garmin. BUT the big drawback was it is not usable with the AW indoors. It requires a GPS signal to even save and upload HR data. This was surprising. I got confirmation of this from their tech support, and also noted on their discussion forum it has been raised for months. They responded that they are aware of the request and will take it under consideration. It is possible to use the Forerunner inside and sync the workout to the Strava site with HR data, but I wanted the option of using either the AW or Forerunner inside. Nike+ Run App Unlike the others, it provides HR analysis without having to pay for a subscription. It also interfaces with Garmin. The big turn-off for me was the website. It was slow compared to the others and was loaded with photographs. Looked pretty like a magazine, but that was not what I wanted. I also could not get HR data onto the site, but did not pursue trying to solve the problem because I didn't like the web site. Runtastic I did not do extensive testing because I found it did not provide a direct link to Garmin. It might be possible to achieve this via third party facilities, but it was not included here: https://tapiriik.com/ Anyway, because of other options, I did not research this further. Runkeeper This seems to fill the bill, but I had trouble getting HR data from AW, so I did not pursue this given the option I went with. By the way, Runkeeper is listed on https://tapiriik.com/ so even if it does not provide a direct link, there is an option. MapMyFitness / MapMyRun from Under Armour I went with this option because it complied with my requirements and everything just worked. Note that the various MapMy apps are driven by the same data base. They differ in some of the default workouts, etc. they provide. The app needed for the AW is MayMyRun which is the app that supports the AW, but that works with MapMyFitness.com seamlessly if you are interested in other sports. In fact, the MapMyRun on the AW gives several types of activities to select when starting a workout. The free version only gives limited HR data, but the MVP option at $30/year provides HR graphs and zones.