Now enters a new app called Field Agent that is free to download but even more, promess to pay you as you use it. Well, sorta, since the pay is not tied to the use of the app per say.
What the app does, is to pull some location based tasks that willing users can sign up to do and get paid for their efforts.
According to the New York Times, they are not even worth doing unless you find yourself in or near the location where the task in hand is to be performed. Generally the tasks consist of filing out a survey, checking the prices of certain products in a store, or taking the picture of products on store' shelves and the pay is around $2 in most cases.
For more, see NYTimes.com