I normally post blog postsabout PKI and not phones. However, I recently received my HTC 8X, which I love. On my previous phones, I had always wanted to track data usage by application. While there may have been apps that already provide this functionality, I was unaware of them. However, my HTC 8X (Verizon), shipped with a app called Data Sense. As, seen in the screenshot below, Data Sense gives me a nice overview of my data usage:

And if I swipe over to Usage it gives me a break down of usage by app. PrettyAwesome !!!

Even more importantly, it breaks down usage by Cellular and Wi-Fi. You can also set usage limits.

-Chris