地図上で円などを描画するときに使えるかなっと思うので
MapView mapView= (MapView)findViewById(R.id.mapId);
Projection projection = mapView.getProjection();
GeoPoint point = new GeoPoint(lat,long);
float distance = 5000; //例:5000m
double radian = Math.cos(Math.toRadians(point.getLatitudeE6() / 1E6));
float pixel = projection.metersToEquatorPixels(Math.round(distance/ radian));