Manual stage reached notification

I would like to receive an email/SMS when a build (particularly a lengthy build) reaches a manual stage. This will allow me to be immediately notified, saving time and some annoyance in having to manually check whether the step is reached, and assist in timely progress when I am away from my system and need to progress a build that has reached that step quickly.

For example: I am out on site, and I need to get back to base asap and manually deploy a build that is urgent.