The latest build of Touchstone does just that. If you have your copy check it out in the Subscription Helper.
Now imagine doing it for MySpace, Facebook, Hi5 etc. The latest build of Touchstone also makes that possible!
Paul has added a feature called 'Subscription Plugins' that allows developers to quickly and easily write little XML files that add Touchstone subscription support to all sorts of services.
Combined with Dapper.net this sort of functionality can be taken to a whole new level - making it easy for users to get alerts from all your favorite web apps - even those that don't support RSS (without the need to write dedicated Input Adapters).
We have included support for LinkedIn already - we look forward to see what the community can come up with. Be sure to email us your plugins.
If you are developer: Read more about it here
Also, since this type of extensibility is a first in the Feed Reading space (as far as we know) we would be interested in collaborating with other feed readers out there to add universal support and working with app developers to build their own plugins for the Subscription Helper. Drop me a line.
Don't have an invite yet? Maybe you should pay more attention.