I just deiscovered there ia a Telegram Action addon.
Maybe another usefull addon would be Threema.
There is already a java-sdk available.
https://gateway.threema.ch/de/developer/sdk-java
Just a thought… 
btw: Where should I open an issue for this request?
Here? GitHub - openhab/openhab2-addons: This is an archive of the full history of the openhab2-addons repo.
That would be great! Threema is my favorite messenger, hands down.
I’m not a big fan of this other messenger, but it really includes end-to-end encryption since today:
I still prefer Threema. Its server is located in Switzerland, where no Patriot Act applies, and, what’s more, WhatsApp will still collect your user data (and merge them with Facebook’s collection of user data).
Fully agree!
Sorry, I meant to say “WhatsApp will still collect your meta data [and merge it with Facebook’s collection of user data].”
I also look for an end-to-end encrypted notification solution. Threema would be very welcome.
I‘ve looked into this today. The API uses the Threema Gateway which requires a (pre-)paid subscription, and it‘s not cheap. See https://gateway.threema.ch/de/products
I honestly doubt there would be many OpenHAB users willing to pay these prices for Threema notifications.
any update here?
the link still describes a business account and I agree: price is too high if just using for private purposes
here’s the answer of Threema Support:
—-
Dear Markus,
Thank you for your message and your interest in Threema Gateway.
In order to send Threema messages from your own environment, some development effort needs
to be done on your part. You can find the technical documentation for your developers
here: API - Threema Gateway. An access to Threema Gateway via the
app is unfortunately not possible.
If you would like to test Threema Gateway, please register for free at
Offer - Threema Gateway. In the test environment is a Gateway ID which can
be only used to test the web interface (GUI). Sending messages via API requires an E2E
Gateway ID. Please request your ID at https://gateway.threema.ch/en/id-request. After your
message, we would be happy to offer you 2’000 credit to start with Threema Gateway.
Should you have further questions, don’t hesitate to contact us again.
—-
Who is interested in such a binding?
I’m considering to work on this