Is it Facebook, podcasting software, the MLB Gameday app? Who knows?
Well, with Onavo you can find out. The main menu displays statistics on your data use over the prior month, and it fingers the apps hogging the most bandwidth. Many of these are obvious, such as any video or streaming app, but I was surprised to see how much data Google Calendar used with its constant synching, and after consulting with Onavo, I decided to synch less frequently
You'll also discover the apps that go online even when they haven't been launched. Don't be surprised to see that many games do this, so if you haven't played them in a while, you might want to get rid of them. Otherwise, those free Android games may end up costing you money if they push you over your data limit.
For international travelers, Onavo can help you avoid (or limit) costly data roaming charges.
And Onavo is actually an app that has more octane on iPhone, for which it will also compress data. (On Android, this feature is currently limited to Ice Cream Sandwich users.)
5. Tether your phone.
So you've signed up for an expensive all-you-can-eat data plan, yet when you try to tether your laptop to your phone to use that 4G connection you paid a premium for, you are stymied. Carriers will try to charge you $20 or $30 a month for tethering privileges, meaning they're trying to charge you twice for network access that you've really already purchased.
For most people, this is more of a nuisance than anything. Wi-Fi is available everywhere, but if you are using your laptop for business, wouldn't it be smarter to stay on a 4G network rather than connecting to an open Wi-Fi one?
On iPhone, tethering is a no-go. On Android, tethering may technically violate your user license, but you can do it, and you no longer need to root your phone. Apps like Clockworkmod's Tether will have you up and running in a few minutes.
Tether isn't a free app, but at $4.99, one stay in a hotel that still charges for Wi-Fi will make this app a no-brainer.
6. Pick your own keyboard.
Siri has been getting all kinds of press lately, and, sure, it can be amusing to try to get Siri to say off-color things. Yet, when I'm using data on my phone, I prefer text-based input.