Request for an SMS setup recommendation.

[deep trench]

I need an offline way to send SMSs, HASS ready. Previously, there was support for USB dongles with SIM800L, but it seems discontinued. I’m looking for a replacement - something cheap and reliable, with only one required feature: the ability to send SMS, external antenna, https or a similar API usable in my local net (not via a device's Wi-Fi in router mode) - good, ability to read SMSs - nice, easy setup - nice.

[strange canyon]

There are web services that offer APIs for sending SMS, like Twilio which integrates with HA: https://www.home-assistant.io/integrations/twilio_sms/.

These are all internet services, though they won't require a special local device

[deep trench]

Thanks, I want it to work without Ethernet or power.

[strange canyon]

I dont know much about SMS but I believe it to be an online only protocol (e.g. only specific companies are authorised to send them, and they will require auth).

Maybe buy an old phone, get a SIM card and then write a custom app to send SMS when something happens (that something could be local)?

[verbal vale]

this has come up before, i think there are some addons that can integrate and allow you to send sms via a modem with a sim. a few people brought it up when core/supervised first got deprecated. its definitely doable but i cant remember specifics

[scarlet glade]

This would be an add-on for Gammu compatible modems:
https://github.com/PavelVe/home-assistant-addons/tree/main/sms-gammu-gateway

[deep trench]

A phone sends data using only a reachable mobile tower. It requires a SIM card and a powered GSM chip, but nothing else. I previously had this functionality (SMS integration, implemented via USB-TTL modem chips like SIM800L, attached an alike device), but it was removed. It is to ensure that critical messages, such as security alerts, can still be sent even when you’re out of power and/or Ethernet even if it is on both sides, even if you are somewhere remote it will be waiting for you to return in a mobile network.

[warped gull]

you can buy sim card, lte modem/router that has api to send sms and UPS to make it work when power is out, that way you will also have backup mobile internet

[deep trench]

A whole modem with a comfortable API is pricey(