I've done enough looking up to now that how this used to be possible on iOS 5.1 and below, and that it's not possible in any version above that.
But how do other apps do it?
So far, I've tried the following (tested on iOS 8.1 simulator, on Xcode):
- (void)turnOnBlueToothPressed:(id)sender {
[[UIApplication sharedApplication] openURL:[NSURL URLWithString:UIApplicationOpenSettingsURLString]];
}
Which opens the app's settings. Not ideal, but it is what it is.
AFAIK, using the following:
[[UIApplication sharedApplication] openURL:[NSURL URLWithString:@"prefs:root=General&path=Bluetooth"]]
No longer works. Alternatively, could anyone point me to the official documentation stating that it no longer works on any version > iOS 5.1?