Not so much my brain, but I'd have to also install it and explain how to use it to my wife, sister-in-law and neighbor who gets the alerts when we are away -- meaning the group that gets the alerts needs to be easily changed too.
I'm interested in alternatives, but the "ease of use" of using your cellphone provider's Email to MMS gateway and the node-red Email node has so far impossible to beat. Only real limitation is that not all providers have the Email to MMS gateway, all the majors do AT&T, Verizon, and T-Mobile, but the resellers are spotty, Ting doesn't, Cricket does for example.
I've tried and given up on Telegram a couple of times, I'll give pushover a try when I finally have enough free time to evaluate it during a 30-day free trial.
My other requirement is when I send a 4K image I want the phone to receive the full 4k image and "pinch-zoom" to work so the person monitoring can make a very fast and easy friend/foe decision.
ntfy is a fairly new notification service. It is open source, free and can also be self-hosted.
Messages are published and subscribed via Topics. If you do this via the ntfy-server hosted by the developer, any other user with the right topic could receive messages from others, because there is no additional password protection. Therefore, you should choose a topic that is difficult to guess.
You can theoretically crypt the text of your messages e2e with a little effort. On Android, you can build something with Termux and for example openssl and Tasker.
If encryption is important to you, take a look at Simplepush which supports end-to-end encryption. It's available for iOS and Android.
You can just choose a password in the app, copy the encryption salt that is also displayed in the app, paste it into the corresponding fields in the node configuration and start sending encrypted notifications.
The app is free to use if you stay under 100 notifications per month.
Full disclosure: I'm the creator of Simplepush.
I just built something similar to Pushover Receipts for Simplepush and integrated it into node-red-contrib-simplepush:
You can define actions for notifications via msg.actions or in the edit view. This will display the defined actions on the notification that you will receive. In the picture below I get three clickable actions ("action1", "action2" and "action3"), if I send a notification to my phone from the flow.
If you enable "forward selected action to output" in the edit view, the action that you will click on will be returned as the output of the Simplepush node.
In the picture below I selected "action2" on my phone for the notification I sent from the flow.
