This project is great, i may be part of this soon as it will be recognize. Good luck! 
You should get in now. Here is how Facebook messenger notifications look like.
Its pretty cool as it keeps all of your notifications in one chat.
https://www.youtube.com/watch?v=lZsAwPDR-E4
No not really signals are maybe in the future. Signals are a diferrent thing, here we provide notifications service where you can keep yourself up to date with prices either with email notifications or with fb messenger notifications for mobile