With Telegram this is pretty simple: "https://api.telegram.org/bot#{token}/sendMessage?chat_id=#{c...

All you'd need to do to set it up is create a bot (from within Telegram via the BotFather account), and then either start a conversation with it or add it to a group chat or channel.

I've been using this approach to send me notifications whenever someone logs in to one of my servers for a bit of extra security.