The Setup Mobile App Preferences feature by default will send a worker push notifications when their client checks in for a service.  If a worker needs to receive notifications for all workers, some workers or doesn't want notifications at all, they can use the Setup Mobile App Preferences to make those selections.

The worker noted on the left hand side is the worker who would receive the notifications.  The worker(s) on the right will be the workers to send notifications when their client checks in.