I'm working on something similar at http://tripovore.com
Basically I think city guides are obsolete (they have been there for 200 years with no major innovation) and have to be reinvented and trip planning automatized using APIs we have online. I currently use 6 of them: foursquare, songkick, instagram, google places, google translate and facebook. I've been working on this for the past 8 months, but I'm having UX difficulties keeping such a complex problem as simple as possible. I first started this during the foursquare hackathon 2011 and the project won the grand prize (called my next trip at that time).
Would love to hear any feedbacks you got at feedback@tripovore.com
Thanks!