For anything less than 24 hours, you can do this:
CONVERT(varchar(8), DATEADD(SECOND, DATEDIFF(SECOND, segstart, segstop), 0), 8)
SELECT CAST('20130906 09:28:00' AS datetime) AS segstart, CAST('20130906 09:37:22' AS datetime) AS segstop
) AS test_data
Edit: Added test data.
SQL DBA,SQL Server MVP(07, 08, 09) Prosecutor James Blackburn, in closing argument in the Fatal Vision murders trial:
If in the future, you should cry a tear, cry one for them [the murder victims]. If in the future, you should say a prayer, say one for them. And if in the future, you should light a candle, light one for them.