Emails when a user gets locked out

This can be done using third party monitoring tools but seeing you are in SBS I'm guessing there may not be huge money in the budget for new software
You may want to check out event triggers
http://technet.microsoft.com/en-us/library/bb490901.aspx
http://windowsitpro.com/article/articleid/44431/pulling-the-event-trigger.html
http://blogs.msdn.com/krichie/archive/2006/03/30/564945.aspx
Those links should get you going.  I haven't tested this fully but it is worth trying out I think.
Thanks
Mike

You can use eventriggers.exe and blat to do this:

Eventtriggers
http://technet.microsoft.com/en-us/library/bb490901.aspx

happy mailing : Blat online
http://www.blat.net/

@echo off
set From=lockout@domain.com
set To=me@domain.com
set SMTP=smtp.domain.com
set Subject=User locked out
set EmailFile=%Temp%\%~n0.eml
>"%EmailFile%" echo A user was locked out at %Date% %Time% on %ComputerName%
"C:\Program Files\blat\blat.exe" "%EmailFile%\%LogFile%" -f %From% -to %To% -server %SMTP% -subject "%Subject%"

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Slight correction: remove the "\%LogFile%" in the last line ...

We use NetWrix Account Lockout Examiner.  

http://www.netwrix.com/account_lockout_examiner.html

It works well for us because it has the option to unlock accounts either via a website (for helpdesk personnel) or email remote control (good for blackberries).

And it was bugging me that the user who was locked out was not reported.
You should be able to combine this with PsLogList to retrieve the event.
PsLogList v2.7
http://technet.microsoft.com/en-us/sysinternals/bb897544.aspx

The new script assumes that the script and the external tools are in the same folder (untested):

@echo off
set From=lockout@domain.com
set To=me@domain.com
set SMTP=smtp.domain.com
set Subject=User locked out
set EmailFile=%Temp%\%~n0.eml
:: *** set the event id of the lockout event eventtriggers is monitoring:
set EventID=
>"%EmailFile%" echo A user was locked out at %Date% %Time% on %ComputerName%; event log entry as follows:
"%~dp0psloglist.exe" -m 1 -i %EventID% security >>"%EmailFile%" 2>&1
"%~dp0blat.exe" "%EmailFile%" -f %From% -to %To% -server %SMTP% -subject "%Subject%"

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I have used Eventtrigers along with Blat. It works fine for a free tool.
You may also take a look at this free tool as well http://www.poweradmin.com/ServerMonitor/features.aspx?show=actions

This seems to be working great. Thanks.