Oops, my mistake. The templates need to be quoted. Try this instead:
- alias: gps_status_x
trigger:
platform: state
entity_id:
- sensor.gps_position_lat_tesla_x
- sensor.gps_position_lon_tesla_x
action:
- service: device_tracker.see
data_template:
dev_id: tesla_x
gps:
- "{{ states('sensor.gps_position_lat_tesla_x') }}"
- "{{ states('sensor.gps_position_lon_tesla_x') }}"