They can range in size from tiny, like the new Jeep Compass, to Texas-sized, like the coming GMC Acadia and Saturn Outlook.

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JiWire is a mobile advertising company that places location-based ads, it calls Compass ads, on mobile apps as well as on Wi-fi service websites in places like cafes.

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Mr Blair (and even his more wonkishly-inclined friend at the Treasury) is like most normal people: he not only lacks such a compass, but wouldn't know what to do with it if he had one.

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