I personally would consider notifications and the ability to run in the background to be essential but there's a better test which is the reason that this exception exists in the first place.

From copyleft.org:

> The system library exception is designed to allow copylefted software to link with these libraries when prohibition of that linking would hurt software freedom more than it would hurt proprietary software.

This is really the core of it -- who is hurt more by disallowing this linking: Google or FOSS apps?