Want a scoring tool like this for yourself?

I want to build a personal tool that scores options I'm comparing — flights, routes, whatever the decision actually is — against what matters to me, not just price.

Here's the pattern I want it to follow:
1. Let me rank what matters to me in order — cost, comfort, flexibility, whatever my real priorities are — and weight every recommendation by that ranking, shown as an explicit breakdown per factor, never collapsed into one unexplained score.
2. Start with a reasonable estimate model if a live data source isn't connected yet, but always label clearly on-screen which mode I'm in — modeled estimate versus real live data — and never present one as the other.
3. Keep anything sensitive, like payment or account details, entirely local to my browser — never sent anywhere or stored remotely.
4. Publish it as a small, real website I can use from my phone, with the scoring logic running instantly, without waiting on a server round-trip.
5. Let me set up a watch on something I care about, with a scheduled check that re-runs itself and tells me about a meaningful change without my having to ask.
6. Keep the backend radically simple — a feature that needs real infrastructure has to earn it, not get added by default.

Please help me scope this into a first small version we can finish today, tell me exactly what you'd need from me at each step (any account access, any purchase like a domain name, anything you can't do without my say-so), and don't do anything irreversible without checking with me first.