The RB can also alert you.
http://wiki.mikrotik.com/wiki/Monitor_i ... B333/433AH
I run the following script. It's sends an email to my phone as a text msg. Put it on scheduler for however often you want to check it. Mine is on 30 minute intervals.
add name=email_voltage policy=ftp,reboot,read,write,policy,test,winbox,password,sniff,sensitive,api source="/system health\
\r\
\n:if ([get voltage]<128) do={/tool e-mail send server=xx.xxx.xxx.xxx to=you@youremail.com subject=[/system identity \
get name] from=you@youremail.com body=(\"Low voltage. Current voltage is :\".[/system health get voltage])} else {:log \
info \"Voltage is ok.\"}\r\
\n"