If you'd like to get running but aren't sure how to start, apps such as Couch-to-5K and Get Running (Couch to 5K) can get you moving gently, and if you're an experienced runner, Ultimate Running Races will help you find challenging courses all over the world. And if, ultimately, you need novelty to get you interested, try Zombies, Run - a weird mix of app to get you running (you can hear the zombies getting closer in your headphones) and game that uses supplies you collect while running to build up your base.
There are lots of apps for cyclists too, whether you want to simply use the iPhone's on-board sensors to map your ride and give you live data about your distance, speed, pace and so on with an app such as Xtrail, administer first aid to your bike on the roadside with Bike Doctor 2, challenge your friends using Strava Cycling, or just find great bike-friendly routes with apps such as London Bike Rides, CycleStreets and Ride the City. Remember to get a secure mount for your device, though.
Swimming's a bit trickier, not just because keeping your device dry is a challenge in itself, but also because it's less easy to track distances automatically. Nevertheless, there are a slew of apps that can help. Swimming Log PRO and its ilk are there so you can record and track your progress, there are apps such as Stroke Builder and Swim Coach Plus to coach you in swimming, and Splashpath can show you where your local pools are and when you can go.
And if churning up and down lanes doesn't sound like your idea of a good time, BeachWeather lets you track conditions at your favourite beaches.
If you prefer the gym, or are forced into one by a lack of local amenities, your iPhone can be a great buddy. Competing with friends and even strangers all over the world can be a great motivator, in apps such as Push-Up Wars and Fitocracy.
The great thing, though, is that you don't need to pay for a gym membership to get started. The App Store is stuffed with apps that will train you. Now, we're not saying that you can't get better and more personalised advice at a gym from a qualified instructor, but if you're worried about making that sort of financial commitment, an app such as Nike mTraining club or DailyBurn (both of which are free) can start you off in your living room, and are a good way to test your resolve.
Again, though, don't just think about exercise in the traditional sense. There are apps for yoga, apps for jiujitsu, capoeira and much more.
Besides, your iPhone can help look after you in more ways than just promoting exercise. If you need a little encouragement to eat more healthily, a recipe app such as Good Food Healthy Recipes can be invaluable, or you can 'gamify' healthy eating with an app such as Munch 5-A Day, which spurs you on to eat plenty of fruit and veg. Of course, long-established weight-loss companies such as WeightWatchers also have apps to complement their services.
If you have a medical condition, search the App Store; there's almost certainly something there that can assist in managing it. And if you're thinking of starting a family, apps such as Period Diary can lend a helping hand.
All of this comes down to the fact that your iOS device can really help with whatever aspect of your personal health and well-being you want to work on. We reckon that the best bit is that you can start gentle - even, in the case of activity trackers such as the Nike FuelBand and Fitbit Ultra, by not changing your lifestyle at all, at least initially - and then, if you think you need to, gently cranking up the intensity.