Add systemd_watchdog to README

Author: Aaron D. Marasco

README.md

@@ -216,7 +216,7 @@ You can then see the notification in action by (re-)starting the service: `syste
 
     $ systemctl --user restart python_demo_service
 
-You can do a lot more via [sd_notify], see its documentation for details.
+You can do a lot more via [sd_notify], see its documentation and [systemd_watchdog] for details.
 
 
 ## Creating a System Service
@@ -292,6 +292,7 @@ We now have a basic implementation of a system systemd service in Python. Depend
 
 * Add support for reloading the service's configuration without a hard restart. See the [`ExecReload`](https://www.freedesktop.org/software/systemd/man/systemd.service.html#ExecReload=) option.
 * Explore the other features of the [python-systemd] package, for example the [`systemd.journal`](https://www.freedesktop.org/software/systemd/python-systemd/journal.html) module for advanced interaction with the systemd journal.
+* To have systemd monitor your service and restart it if it hangs, a Python wrapper for [sd_notify] is available called "[systemd_watchdog]."
 
 And of course, if you find an error in this tutorial or have an addition, feel free to create an issue or a pull request.
 
@@ -307,5 +308,5 @@ Happy coding!
 [systemd.service]: https://www.freedesktop.org/software/systemd/man/systemd.service.html
 [systemd.special]: https://www.freedesktop.org/software/systemd/man/systemd.special.html
 [systemd.target]: https://www.freedesktop.org/software/systemd/man/systemd.target.html
+[systemd_watchdog]: https://github.com/AaronDMarasco/systemd-watchdog
 [useradd]: https://linux.die.net/man/8/useradd
-