I built RivalFlag — an AI-powered competitor monitoring tool for indie founders and small SaaS teams. Total cost so far: $10.46 (just the domain). Here's the full breakdown of what I built, the stack, and what I learned.
The Problem
Enterprise competitive intelligence tools cost $20,000+/year. They're built for sales teams at Fortune 500 companies, not for a solo founder who just wants to know when their competitor changes their pricing page.
The budget alternatives? Most are basic change-detection tools — they'll tell you something changed on a page, but not what it means. You end up drowning in noise alerts about footer text updates and cookie banner changes.
I wanted something in between: AI-powered analysis at an indie-founder price point.
The Stack
Here's what I used — all on free tiers:
| Service | Role | Cost |
|---|---|---|
| Next.js 15 | Full-stack framework | Free |
| Vercel | Hosting + edge functions + cron | Free tier |
| Supabase | Auth + PostgreSQL + Row Level Security | Free tier |
| OpenAI (GPT-5.4-nano) | Change analysis + digest summarization | ~$0.002/analysis |
| Resend | Transactional email (weekly digests) | Free tier (100/day) |
| Cloudflare | DNS + domain ($10.46/yr) | ~Free |
| Tailwind CSS | Styling | Free |
Total infrastructure cost: $10.46 (just the domain).
How It Works
1. Add a Competitor
Drop in a URL. The system automatically discovers their key pages — pricing, features, blog/changelog, about, and careers.
2. Daily Scanning
A Vercel cron job runs daily. For each monitored page: fetch current content, compare against the last snapshot, detect changes with structured diffing, classify severity (critical/high/medium/low).
3. AI Analysis
Instead of just saying "47 lines changed on /pricing," the AI analyzer reads the diff and produces strategic insights — not just what changed, but why it matters and what you should do about it.
4. Weekly Digest
Every Monday morning, you get an email summarizing all competitor changes from the past week. AI-generated executive summary, categorized by importance, with action items.
Key Technical Decisions
Why Supabase? Row Level Security. Every query is automatically scoped to the authenticated user. No multi-tenancy bugs possible.
Why GPT-5.4-nano? Cost. At $0.002 per analysis, I can analyze 100 page changes for $0.20.
Why not RSS or Google Alerts? Most SaaS pricing pages don't have RSS feeds. Google Alerts misses dynamic pages. Direct scraping + diffing catches everything.
Lessons Learned
- The product isn't the hard part. I built the entire app in a few days. The hard part is distribution.
- Competitive intelligence for CI tools is recursive. I found 7+ indie competitors building the same thing. Market is real but crowding fast.
- Free tiers are incredible in 2026. Vercel + Supabase + Resend + Cloudflare = production SaaS for $0/month.
- SEO is a long game, but start day 1. Every day you wait is a day later it starts compounding.
Try It
If you're a SaaS founder who wants to know what your competitors are doing — without checking their website every day — check out RivalFlag.
Currently in early access. Sign up and I'll set you up manually while we're in beta.
Building in public at @RivalFlag. Ask me anything in the comments.
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