Sometimes an app can be a feature that is missing from the OS, or a feature that isn't well implemented in the OS. Flashlight apps are a great example.
Another example are apps that track mobile data usage. If you have unlimited mobile data, you might not care how much mobile data you are using. That's my behavior when I am at home.
But when I travel, I am either using a prepaid mobile data card (which is what I am doing now – 1GB for 48 krone/$8US), or using a mobile roaming package from my US carrier (my wife and kids are on a 800MB roaming plan from ATT Mobile).
In either case, it is critical to know how much mobile data you are consuming, per day, per week, per trip, and per plan term.
My favorite app to do this is called My Data Manager and it is free and available for iOS and for Android.
My Data Manager has three tabs to show you how much data you are consuming on your carriers's mobile data network, how much data you are consuming by roaming on other networks, and how much data your are consuming on wifi. It also shows you what apps are consuming the most data for each tab.
You can set up your mobile plans in the app so you can see how you are doing for the current plan term.
I have been in europe since Monday morning (four days now) and I have consumed 128MB on my prepaid 1GB danish sim and I have consumed 155MB on wifi. I haven't had to roam since I have a local data sim. My wife and kids have similar data usage except that they are all roaming on other data networks and are well within their 800MB cap.
If you have a cap on your mobile data usage or if you are roaming on other data networks, I highly recommend getting My Data Manager to keep track. Mobile data is expensive when you go off plan or above plan. Keeping track gives you peace of mind and that's a valuable thing.
