iOS Background Mode
I have a question about running an app in the background. I know about how to do it, but Apple does not like the way I'm doing it.
To get you on the same page, I have a security app, and I need to it monitor the device even when it is in the background. It is sort of like a burglar alarm. I was using background audio mode, thinking it would be okay because I will be playing a sound when it is triggered. Needless to say, Apple didn't like that. So I added a ping! It pings while active, therefor playing background audio while in the background. Once again, they didn't like that either.
My app monitors the accelerometer as well (but not always, only when chosen by the user).
My question is, how are apps like Skype, and other similar apps able to turn the status bar red, and stay in the background? (Even some alarm apps will do this, without playing any audio or anything).
Also I can't use the notification system because it does not update fast enough if I'm monitoring the battery level. For my app I need immediate response.
I have also searched around tirelessly for this answer before I posted my question (the answers I have found, do not work for me..) :(
I would greatly appreciate any insight on this, Thanks in advance!
(If you need anymore information, please ask!)
Answer
From what I can tell from their documentation, it seems that the only way you can maintain a persistent background connection is by using one of their seven background mode keys, which I can see you've been trying since you registered for background audio. I know some alarm apps as well that use this feature (e.g. Sleep Cycle), and my assumption is that they are also using background audio mode, considering the other six modes are not remotely close to what they would need it for.
I think Apple's reasoning might be that these apps are allowed to do so, because their app is designed to be used when the user is not using the phone actively (i.e. when they're sleeping), and requires the audio to wake the user up, whereas if you are running a security app that wants to be active at all times, it may interfere with other features the user may use like Skype. The red bar will also persist at the top of the device at all times when the user is using it, which they may mistake for something that is still playing since usually when a red bar appears it means to the user that they are still actively using something. Again, I think wake-up alarm apps and others like them that aren't using persistent audio are able to get away with this since they are designed for use when the phone is inactive, so having the persistent red bar when the app is not visible is less of an issue.
In some other cases, like Nike+ (discussed here) and likely pedometers, they seem to be using the location background mode, since they often also track where you went and need to know distance. In that discussion I linked to, it looks like others were able to get accelerometer updates by registering for a background mode that applied to them. Have you tried registering for location movements? One downside I can see to that is it might drain battery life quicker, but if you check location infrequently it might not be too bad? Another is that I don't think you can directly play audio when in location background mode, but you could try to trigger a sound notification? :) That might be a nice workaround for it if that works for your app.
Again, the reasoning I have for why these apps are able to do it is just based on how I've seen other apps operating, and Apple may have different reasons for why it accepts them, but that was my best way of thinking why your app got rejected for using those modes while the others are able to do it. If location isn't what you're looking for, unfortunately I'm not sure from what it sounds like your app is doing that you'd be able to operate it continuously in the background in the way you're expecting.