I was looking for the same thing but I have find nothing.
BUT I have an app from the Play Store (MacroDroid) that is able to intercept any notification and say with TTS the contents ... How can they do this ?
Erel, yes! You are right ! it's an accessibility app.
Also PushBullet can install itself as accessibility app and send all the received notification (from any app running on the terminal) to another device (i.e. an app running inside Chrome on a PC)
Can we build an app like MacroDroid or PushBullet that install a service *under* Accessibility interface ?