One day, not long after Siri debuted on the iPhone 4S, I randomly checked the data usage on my AT&T wireless bill and gasped. In one month, I jumped from less than 1GB of data consumption to 2.3GB. In hindsight, I should\u2019ve seen it coming. But Siri was new and cool, and I wanted to test her everywhere I went.\n\tI learned my lesson. Still, in this day of tiered data plans, I can\u2019t seem to shake the nagging feeling that I'm always about to blow past my monthly allotment. That\u2019s why I have high hopes for Onavo Count, a new free app for iOS and Android. The app monitors 3G\/4G\/LTE data usage by app on your device, and the developer says it doesn\u2019t drain your battery.\n\tOnavo Count gives you a 30-day overview of your app data consumption, ranks apps by usage and displays usage in attractive charts and graphs. This is more or less the same concept promised in the\u00a0Windows Phone 8 Data Sense feature\u00a0that was\u00a0announced this week.\n\tI haven\u2019t used Onavo Count for long enough to comment on its effectiveness. But I can tell you this much:\n\t\n\t\tOnavo Count looks to be a whole lot more useful than My AT&T, the AT&T app I've used in the past to check my data usage. AT&T\u2019s app doesn\u2019t offer an app-by-app breakdown, nor does it provide alerts beyond telling you when it\u2019s time to pay your bill. Onavo Count, in contrast, provides helpful usage notifications.\n\t\n\t\tThe Android app offers more features than the iOS version, mostly due to the differences between the two operating systems. With Android, you get three widgets to keep you posted on data usage, including a widget that display which apps are consuming data in real time. You can also restrict certain apps to Wi-Fi, such as Pandora or other streaming content apps, a setting I didn\u2019t see in the iOS app.\n\n\tOnavo Count also works with Onavo Extend, a free, standalone iOS and Android app that compresses cellular wireless data so you can get more out of your allotment.\n\tOnavo Count isn\u2019t your only option for tracking cellular data. The Google Play Store in particular has several such apps, including the free Network Counter. Whichever platform you use, give Onavo Count a try. You might even be able to talk to Siri without data-overage paranoia.