I just tried my first recipe with Joule (it was fun!). When it was done I heard a very faint sound from the Joule app, which was in the background, and that was it.
I was expecting the app to not make a noise itself and instead to send a notification. This looks like a feature on the iOS app but not the Android one. Could you add this? This is the right way to do things, and on Android your notification could do cool stuff like have a "Stop" button to stop Joule.