If they have a decent API (like MutluSMS. Very good documented and the person who made the request was so kind to translate all the stuff for me), someone is willing to act as a tester and translate stuff it is no problem.

If I have to scrape the Website like I do with o2online and Vodafone it is not possible without an account.

So providers without a decent API can only be added by people who have an account for the particular provider and some python knowledge.