I want to track a vehicle fleet. Whenever the device enters into the specified geofence, it should fire a text message to the specified mobile numbers, so that they will get notified.
You don't need a specific application to do this: it can be done with Tasker. Use the AutoLocation plugin to set up a geofence event. In Tasker, create a profile "enter depot" (or whatever the area is), where the event is entering the geofence you defined, and the task is to send an SMS. (You can find "Send SMS" under the "Phone" action category.)
I'm sure you can set up something similar using Automate or another automation app. I just know how to do it with Tasker because that's what I use.