Zapier has become one of my favorites web services. I've always lamented that IFTTT doesn't cater to the productivity/project management crowd by offering a very limited set of channels to work with. Then Zapier came along and blew me away.
One of my favorite bits of Zapier happens when you want to wire up services they don't support: they actually ask you for an email address to notify you when they do support it. And yet almost nobody else does.
More impressive (although this is, to be fair, a low bar): they do not try to stick you on a mailing list or anything like that.
A desktop program that does something like Zapier would be useful and not terribly hard to make. I simply would not trust an online service to hold some credentials.
I've automated these sorts of tasks many times with Python scripts but never made a general solution with a nice GUI.
Create a nice responsive GUI to manage the scheduling and allow the community to submit Python plug-ins to do specific tasks. API keys and credentials will always be stored on the user's computer only.