That's actually an RF testpoint, not an SMA connector (by which I think you mean UF.L connector, like this guy: http://upload.wikimedia.org/wikipedia/commons/c/ca/U.FL_conn...). It functions like a switch that is closed when the RF tester connects to it.
In a sense, you're right - it's meant as a quick release testpoint for conducted radio performance on a manufacturing line. Theoretically, you COULD hook up an antenna to it, but you'd have to know some substantive details about the integrated PCB antenna (impedance, center frequency, etc) to get good or even comparable performance out of the external one. Probably not to a male UFL connector, in any case - I'm 99% sure this type of connector is not compatible with UFL.
Mileage may vary, of course, but in my experience this type of connector is more frequently used to get conducted power RF measurements in manufacturing settings.
