Weightwatchers has an app too, which has all the bells and whistles as its website. You don't have to be a member to download but you will only see a sample of the app.
MyFitnessPal is an app that combines food and exercise. It is a diet and fitness community so again you can receive peer support. It's an app that I know many people swear by in keeping themselves on track.
Apps aimed just for fitness include runkeeper and Map My Run. These track your exercise, including how fast you're running, as well as giving you your final distance.
Couch to 5km aims to get you to do just that - get from the couch to run 5km. It has been around for a long time with proven results.
If you need a bit of a boost then why not download Bootcamp. You can build your own workout from 40 different exercises and get motivated just like you would at the gym. There are four sections, total boy workouts, upper and lower body and core body workouts. It also has music, though you can use your own tracks in its place.
And if you decide you need a bit more support than what an app can give you, search on Facebook for such groups.