You could create a job to run every so often to check the total_elapsed_time in sys.dm_exec_requests and send an email if a long running process is found. Something like
IF EXISTS (SELECT COUNT(s.session_id) FROM sys.dm_exec_sessions s
INNER JOIN sys.dm_exec_requests r ON s.session_id = r.session_id
WHERE r.total_elapsed_time > 10000 AND s.group_id > 1)
BEGIN
Mail or whatever goes here
END
Of course how many milliseconds that r.total_elapsed_time should be set for and how often to run the job is something you'll have to decide.