Live traffic comes from adsb.lol, which doesn't let web pages read its data directly. When this page is hosted with its relay file (_worker.js on Cloudflare Pages, or _redirects on Netlify), your own site passes the data through and nothing else is needed. Otherwise it goes through shared public relays (test.cors.workers.dev, cors.eu.org, allorigins.win), which get busy and drop out, or through a relay you run, whose address you can paste here. A full URL with {lat}, {lon} and {nm} also works.
Weather: NOAA HRRR and GFS via Open-Meteo. Terrain: Mapzen terrain tiles on AWS. Imagery: Esri, Maxar, Earthstar Geographics. Aircraft: community ADS-B networks. A planning aid only: check official weather briefings before you fly.
Browsers only allow sound after you tap something, so press one of the sound buttons once each time you open the app. Keep the app open and in front: phones pause web pages when the screen locks or you switch apps, and alerts stop. While the alert is armed the app asks to keep the screen on. The zone follows the probe. For dependable alerts, host the app with its relay file (_worker.js on Cloudflare Pages, or _redirects on Netlify).