Microsoft managed to hold some key features back for the launch of Windows Phone 8, among the most intriguing of which is Data Sense.

It offers users an overview of mobile data use, showing which apps have been using most data, and allowing users to set a data limit so the app can sound the alarm when you’re about to breach the cap. And the app has a Live Tile you can pin to the phone’s homescreen, displaying a running total of data consumed over the past month.

Now I’m sure you’re thinking this is nothing new – and you’d be right. There are plenty of apps offering similar features on both iOS and Android, and integrated tools as well, but none couple it with the ability to compress web pages as they’re delivered over the mobile network as Data Sense does.

Handily, this compression kicks in automatically as the data limit you’ve set is approached. And it has not only the potential to help users on low data caps eke more browsing time out of their monthly contracts – 45% more compared with the same data plan on a phone without Data Sense enabled says Microsoft – but it could also help prevent swingeing roaming bills.

Alas, there is a major gotcha with Data Sense, and that is it requires operator buy-in to be included, with only US network Verizon on board so far.

In other words, if your mobile network of choice decides it would rather you ran up a big bill because you haven’t realised you’ve gone over your limit, it’ll block the feature. That’ll be most of them, then.