Read GPS Coordinates into LineString from Table
You can use dynamic SQL to build the string to feed into STGeomFromText(). I don't think you'll be able to do it relationally (though, to be fair, this is not my expertise). This will get you going until (if) something better comes along.

declare @Geo table(long float, lat float)
insert into @Geo(  long, lat ) values
               ( -121.527200, 45.712113 ),
               ( -121.517265, 45.714240 ),
               ( -121.511536, 45.714825)

DECLARE 
  @cols NVARCHAR(MAX) = N'', 
  @sql NVARCHAR(MAX) = N'DECLARE @g GEOGRAPHY;
     SET @g = GEOGRAPHY::STGeomFromText(''LINESTRING (';

SELECT @cols += N',' + RTRIM(long) + N' ' + RTRIM(lat) FROM @Geo;

SET @cols = STUFF(@cols, 1, 1, N'');

SET @sql += @cols + N')'', 4326);'

SELECT @sql += N'SELECT @g.STPointN(' + RTRIM(ROW_NUMBER() OVER (ORDER BY long))
  + N');' FROM @Geo;

PRINT @sql;
EXEC sys.sp_executesql @sql;