Here are the Libraries I found
http://curved_lines.overfx.net/ Dead link
http://www.geocodezip.com/v3_polyline_example_rhumb.html
http://www.geocodezip.com/v3_polyline_example_arc.html
Actually I just found that Google map Polyline takes in a list of point to construct. So u can pass in multiple points to make the line looks curved.
PS: u can use the draw arc function in the 2 links below to get the list of points for drawing