Free iPhone app: Databit (Normally $1.99)
Databit is the simplest yet powerful app to track your data usage. Just open the app or take a look at the Notification Center to know exactly your data consumption and avoid nasty extra charges in your mobile plan.
Features:
• Real time metrics. No need to call your carrier anymore.
• Widget. Get your data usage right on your Notification Center.
• Automatically reset the data on the billing day.
• Calibrate the app manually if needed.
• Minimalist design. No useless information in the screen.
• Works for all carriers.
• Track LTE, 4G & 3G
• Ideal for Personal Hotspot measuring