Put circle over google map

I have map ( GeoActivity ) in my app. I need to开发者_StackOverflow mark some region with circle, circle need to move with finger touch . How to achieve that ? I need something similar like http://www.apartmentfinder.com/Georgia/Atlanta-Apartments when you go on personalize your search .

Any idea, advice ?

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have you looked at following post Creating Custom Overlay on the map