Clearly there are a lot of startups in this space.
Just posted BubbleGlobe yesterday that does something similar.
Also added Embark to my Tours/Activities with locals collection: http://www.producthunt.com/@anuj...
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I actually know the people who created this so I might be biased, but the look and feel of Embark.org is so much more beautiful and easy to use than a lot of the other sites doing similar things.
GrowthHackers