You can use an animated gif as the marker icon to simulate the blue circle.
The location accuracy depends on the service that is used to get the current location. The built-in functionality unfortunately does not provide the accuracy of the result.
Unfortunately the blue dot which you are referring to is not supported in the Google Maps API at this time. This is why I suggested to simulate the behaviour with an image.
We are not aware of any other location sensors for Delphi at this time. We'll have to investigate if it is possible to implement an alternative location sensor in a future version of TMS FMX WebGMaps.