I hate this setup.
Rasp. Pi Pico W has a Wi-Fi card. Cool. The WiFi connects to your local WiFi network, which connects to your ISP, which connects to the internet, which connects to ntfy.sh. NTFY.sh then creates a push notification over Apple and/or Android, then finds your Phone, likely realizing your phone is currently in your WiFi network. It then sends a message to your ISP, to send a message to your WiFi network, which sends a message to your Phone and you finally get the alert.
Its probably the easiest way to get things done, but a bluetooth alert and/or Wifi-direct alert of some kind would be better. Phone APIs don't seem too keen on WiFi / Socket servers however. Bluetooth would likely be a better solution, but involves pairing and other such noise to complicate the process.
Hmmmmm. I see that ntfy.sh is the easiest way to bridge it all together. But that doesn't mean I have to like it.