For mine, I just used a $1/mo VPS with a cron job running a bash script that used curl to poll the parking system and determine if its response was interesting. I used "copy as cURL" from browser dev tools to find something usable (which incorporated a slightly fragile, but very long lived, session token corresponding to my "cart") and I actually had to use curl-impersonate [0] for Cloudflare bot detection to stay out of my way. And then curl to alert me via Pushover.
