Get NULL statistics for a column in MS SQL Server
Nothing so easy. You would need to use DBCC SHOW_STATISTICS and look at the histogram, taking into account that the statistics might be filtered or multi column.
Probably easier to just let SQL Server do it and generate an estimated execution plan for the statement select * from foo where bar is null SQL Server will then use appropriate statistics if they exist or create them if they don't (assuming that the auto create statistics option is enabled).
You can then look at the estimated number of rows going into the SELECT iterator (This shows up as StatementEstRows in the XML for purposes of parsing programatically)
Example code
/*Create temporary stored procedure with query of interest*/
CREATE PROC dbo.#plan_test
AS
SELECT *
FROM master..spt_values
WHERE low IS NULL

GO

/*Generate an execution plan*/
SET FMTONLY ON
EXEC dbo.#plan_test
SET FMTONLY OFF;

/*Retrieve the plan and parse the estimated rows*/
WITH  XMLNAMESPACES ('http://schemas.microsoft.com/sqlserver/2004/07/showplan' as sql) 
SELECT  query_plan.value('(//sql:StmtSimple[1]/@StatementEstRows)[1]', 'float') AS EstimatedNumberOfRows
FROM sys.dm_exec_cached_plans 
CROSS APPLY sys.dm_exec_sql_text(plan_handle) 
CROSS APPLY sys.dm_exec_query_plan(plan_handle) 
WHERE sys.dm_exec_sql_text.objectid=OBJECT_ID('tempdb.dbo.#plan_test') 
     AND sys.dm_exec_sql_text.dbid=2

DROP PROC dbo.#plan_test