I've had voice notification of someone at the door well before Alexa.
This was done with a PC a motion sensor.
Getting Alexa to speak a specific phrase is beyond my know how.
However it may be possible with IFTTT
![Huh ???](https://www.echotalk.org/Smileys/default/huh.gif)
being outside the US I can't use Alexa with IFTTT.