This is a simple implementation of binary sensor which checks the presense of IP address in network.
Copy this folder to <config_dir>/custom_components/ip_sensor/.
Add the following to your configuration.yaml file:
# Example configuration.yaml entry
binary_sensor:
platform: ip_sensor
scan_interval: 5
hosts:
router: 192.168.2.1 # device => binary_sensor.router
toshiba_tv: 192.168.2.149 # device => binary_sensor.toshiba_tv