You can do something like this (FusionTableLayer example):
layer = new google.maps.FusionTablesLayer({
query: {
select: 'geometry',
from: tableId,
where: 'ST_INTERSECTS(geometry, CIRCLE(LATLNG(' + lat + ', ' + lng + '),1))',
limit: 1
}
Checks for the intersection of the polygon defined in the geometry column and a circle at lat,lng with a diameter of 1 meter.