My entire family is noticing very high data usage since upgrading to iOS 8. Two iPhone 5S's, an iPhone 5, my iPhone 6 and my LTE iPad Air. We have all been using iOS 8 since it lauched and upgraded to 8.0.2 when it was pushed out. There must be some part of the OS that has gone rogue. My iPad Air has not left the house (and wifi) since upgrading to iOS 8 and has used all of it's 200MB data in two weeks (typical usage 40MB a month). I am having to be very concsious of my iPhone 6 data usage to avoid going over my 5GB this month. I don't do any streaming audio/video and somehow I'm using 100-200MB a day. Mild safari/iMessage/Maps usage daily. All of our phones spend most of their day bathed in wifi. I upgraded to iPhone 6 the day after my plan rolled over over and I had my cellular statistics reset the day after that. There's over 1GB of data that is unaccounted for. I have checked all the usual culprits: background updates and app refresh. All the settings are the same from iOS7 Something is up here. I hope 8.1 solves this issue.