He explains how exactly he pulled it off in his post here.
In Fred’s case, he needed this for a presentation at a geolocation conference, but I can see this being applied in many uses. One of the foremost being a way to align your personal finance spending patterns & what your goals actually are. Imagine you “think” you’re being pretty good at reducing your nights out drinking or eating but the actual FourSquare check-ins show otherwise. If you’re honest with yourself, you’d be able to take stock and change more of your habits to less expensive outings like free art galleries and park picnics.
How else could we use this new mashup to benefit or improve our personal lives?