The most direct way would be to use mail or mailx to send a mail from the commandline - since the address is most likely always the same, you could write a brief wrapper script to handle that and only have to pass it the message as argument.
Example that can be tried from the commandline:
echo "here goes your text" | mail -s "GTD by mail" email@example.com
If you're fancy and want individual subjects for each mail, you can give the wrapper script two arguments, subject and body.
A slightly more complicated but highly reliable setup would be what I'm preferring: set up the system logging daemon (syslogd) to file messages of one selected facility not only to logfile, but also to mail. I'm using that for everything from network-wide configuration change messages, working hour and activity logging, and an idea/todo log.
This gives the added benefit that all machines on the network can be told to send those messages to one loghost, and use that loghost for reference.
See here for a description on how to reroute syslog messages to mail.