Hi,
You can now send WhatsApp messages using a free API:
https://www.callmebot.com/blog/whatsapp-text-messages-from-homeassistant/
The service is still in beta version but it is working well with a small delay (10 seconds aprox.)
It is super easy to use.
How long does it takes to get the apikey?
EDIT: Nevermind, I have just got it. It was my mistake. I test it and it is working fine 
No. Only text messages for now.
I did a test.
It works with API test, but doesnât work with HA.
What am I doing wrong?
This is my code:
notify:
- name: WhatsApp
platform: command_line
command: 'wget $(cat) -O /dev/null'
automation:
- id: '1591454222374'
alias: Rega Ligada Notif
description: ''
trigger:
- entity_id: switch.rega
from: 'off'
platform: state
to: 'on'
condition: []
action:
- data:
message: http://api.callmebot.com/whatsapp.php?source=HA&user=myphonenumber&text=Rega+Ligada&apikey=mykey
service: notify.WhatsApp
Hi @Joca , there was a mistake in the instructions. use &phone instead of &user in the url.
message: http://api.callmebot.com/whatsapp.php?source=HA&phone=myphonenumber&text=Rega+Ligada&apikey=mykey
Instructions updated 
Now is working.
Iâll be waiting for the the delay correction
Sending photos and videos would be also an excellent improvement.
Nice job!
Thanks.
It is a matter of resources⌠I try to minimize the costs but it is not easy⌠The hobbie is turning expensive. 
I donât mean this the wrong way, but what are the security implications of this? Is there any way that this system could be abused?
Genuine question as it would be quite handy to have notifications in Whatsapp, but Iâm not tech savvy with respect to how secure it is etc.
Anyone using this in Nodered? Just wondered how this would be done.
Each user (phone number) is having their own private apikey to allow sending messages only to that phone number (who requested the apikey). So basically you can only spam to yourself.
Awesome - cheers for that clarification.
Okay - managed to get this going and testing things out. I can (nodered) send a test message using the âhttp requestâ node.
Now I ned to get a little more complicated. Iâm trying to work out how to add data from a sensor into the message.
Currently I have this in a template node where {{service}} contains the battery percent:
{ "domain": "notify",
"service": "mobile_app_pixel4",
"data": {
"title": "Plug Tess in",
"message": "You forgot to plug in Tess. The battery is at {{service}}%"
}
}
Any idea how I would make that work with with Whatsapp?
Just worked this out - so the âhttp requestâ node allows you to use mustache-style tags in it. This way, the relevant data can be pulled from sensors etc.
An example of the url in the node would be:
https://api.callmebot.com/whatsapp.php?phone=MyTelephoneNumber&text=This+is+a+test+{{state}}&apikey=MyAPIkey
using nodered on HA - i have a function which returns msg to the WhatsApp node.
in the WhatsApp notify node i have this. but i only get This. i dont get info within msg that was sent from function {
âmessageâ: âhttps://api.callmebot.com/whatsapp.php?phone=+mobilenumber&text=This+{{msg}}&apikey=apikeyâ
}
i have alexa node from same function node and it is picking up the msg info.
any help to display msg info in WhatsApp?
New boy here - just set this up. had a bit of trouble with formating but figured it out - THANKS for such a great service. really useful, pretty easy to setup. Look forward to enhancements
The service now is not free! 
No surprise there. Itâs the direction all weather service providers are taking. I wouldnât build my system around the expectation of any service remaining free these days.
If you canât afford to pay $4 per year, you can contact the owner and he will find a solution for you. Thatâs what he said in the webpage.
I canât see anywhere that says itâs not free. In fact I just set this up last night and itâs still working fine right now⌠where are people seeing that itâs not free?