I'm currently building a project to enable passive communication using several Flic buttons and Wear OS watches. I currently have an Android app up-and-running where one can scan for new Flic buttons, connect them, associate the button to a connected bluetooth device and then save the association. My current problem is that I can't get the actual notifications to work, I can successfully send them but they are not received by the Wear OS watch. In my current setup I'm using bluetooth but I would like to migrate this to send the notifications directly over the network since there will be 10+ watches receiving notifications.

Here is an outline of the user-flow/requirements of the app:

1. A user should be able to connect a new Flic button.
2. The user can choose a Wear OS watch to associate with the button
3. The user can see the associated button and watch on the home screen and rename the association, for example as "Room 1"
4. The user can choose different vibration patters for the three types of button clicks on the Flic button: single, double, and hold.
5. When the button is clicked a vibration corresponding to the chosen pattern is sent to the watch to notify the wearer.
6. The user can choose to connect more buttons and watches to repeat the process for other rooms at the hospital.

Requirements

• A user should be able to associate several buttons and several watches with each other
• The notifications should be sent directly to the watch since there will be several watches connected to the same phone/WiFi.
• It should be easy to choose which vibrations patterns to associate with the different types of clicks of the Flic button
• It has to be low latency and reliable

I've been trying to get it up-and-running with Firebase Cloud Messaging but I still can't seem to receive the notifications. Any ideas on how to solve this and ensure that the notifications are sent directly to the watches?

I've tried using the Data Layer API but regardless of my setup I can't seem to get it to work. Now I'm contemplating if I should use FCM but I don't really know if that's the easiest/best way to build it.