I have missed the WTH month so i will just post a new feature request.
Template and rest platforms both support many types of entities: sensors, binary_sensors, switches, etc, but not device_tracker.
But for example MQTT platform does support device_tracker sensor, so it should be possible to add similar support to rest and template platforms.
Currently, to ccreate a new device_tracker entity, we need to send latitude and longitude values to MQTT and create MQTT device_tracker sensors fetching the data back from MQTT, what feels awkward.