[calcsam]

See IFTTT, Zapier, etc. They are doing what you're doing; maybe you can build on top?

[JohnQUnknown]

I thought about using one of such services, but I think they're way too general(ist?) for me, what I want to do is basically have a way to either send a message, login to a panel and submit a message from there or schedule a message that will be distributed among several "subscribers" via different methods, like a newsletter system but using a method selected by the end-user (SMS, email, twitter, etc.)

But you might be right, I could probably do something similar on top of IFTTT, Zapier or Yahoo! Pipelines...