Get more data on your iPhone or Android's wireless plan for free

Image courtesy of Onavo

Unless you are one of the lucky few to have an unlimited, all-you-can-eat wireless plan, your phone's data is limited -- it's either metered, where your rate depends upon how much you use it -- or capped, where your data simply stops when you hit a predefined limit.

But what if you could install an app on your phone that extended the value of your existing plan automatically, giving you lots of extra data at no additional cost?

You'd probably snap that up in a heartbeat. And indeed, Onavo is an app that compresses your mobile data in the background to dramatically increase the value of your existing data plan.

I tried Onavo on my iPhone, and found that it worked as advertised. The app is free (for now -- eventually, the company claims to be moving to a pay model) and requires no particular setup to get started. It's smart enough to go offline when you're using a Wi-Fi network, but when you're using your phone's service plan, it kicks in and compresses your incoming data -- including email, photos and video -- by as much as 80 percent.

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You'll notice a few changes using Onavo. Some graphics might appear somewhat pixelated due to the compression, and email arrives in plain text format. You can mitigate both: every message comes with a button to download the full, original version, for example, and you can throttle the level of compression if you want higher (or lower) quality graphics.

Want to know how you're doing? Onavo tracks your data usage and estimated cost savings, and can generate reports for you whenever you would like to assess not just your overall usage, but how you're spending your time online. It shows your usage of iTunes, Web, email, YouTube and other services.

The bottom line is that Onavo effortlessly extends the value of your existing data plan, which can come in especially handy if you are on the road a lot. You might find it necessary to tweak your settings a bit, but it can be well worth it to avoid higher phone bills.