New Product Opportunities — Devin Booking System

_Discovered: 2026-07-28 from How I Built a Full Booking System as a Side Project — With Devin as My Engineering Partner_

_Supplements the main Product Backlog_

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14. GymClass — Martial Arts Academy Booking SaaS

Confidence: 8/10 | Difficulty: 6/10 | Seed Fit: 4/10 | Asymmetric Upside: Yes

Problem

Small martial arts academies and gyms are underserved by existing booking management software. Mindbody is too expensive ($200+/mo minimum) and enterprise-focused. ClassPass is consumer-facing, not academy management. Spreadsheets don't scale. Academy owners piece together scheduling, attendance, payments, and communication — none integrated.

Evidence: The How I Built a Full Booking System post describes: "A full-stack booking system for martial arts academies. TypeScript, Bun, React, Hono, tRPC, Drizzle ORM, Neon Postgres, deployed on Cloudflare. Multiple user roles (admins, coaches, students, parents), class scheduling, attendance tracking, trial bookings, family account management, membership plans with booking limits." Confirms real usage: "This isn't a toy project. It's a real app with real users at our academy." Lists 9 completed feature categories.

Users

Martial arts academy owners (BJJ, Muay Thai, Judo, Karate, etc.) | Small gym owners | Independent coaches | Studio owners needing family accounts

Solution

A SaaS booking platform for martial arts academies with core features already built and production-tested: class scheduling with materialization, attendance tracking with role-based access, trial booking, family/parent-child accounts, membership plans with booking limits, attendee visibility, WhatsApp trial connector (research phase).

MVP

The working app is the MVP. Package it as multi-tenant SaaS: one codebase, tenant-per-academy, self-service onboarding.

Distribution

Launch via author's own academy | Case study: "How My Academy Replaced Spreadsheets" | Martial arts forums (r/bjj, r/martialarts) | BJJ YouTube channels | Gym equipment partnerships

Pricing

Free tier: Single coach, 30 students, basic scheduling. Pro ($29/mo): Multi-coach, family accounts, attendance, membership. Academy ($79/mo): All roles, WhatsApp booking, trial management, analytics. White-label ($199/mo): Custom domain, API access.

Competition

Mindbody ($200+/mo, bloated) | ClassPass (not management) | ZenPlanner (dated UI) | Spreadsheets (status quo for small academies)

Differentiation: Built by a martial artist for his own academy. Modern stack (Bun/Hono/tRPC/Cloudflare). Family accounts as first-class feature. WhatsApp integration.

First Experiment

Landing page with demo video. Show to 5 academy owners: "Would you pay $29/mo for this?"

Roadmap

Tenant isolation | 2. Self-service onboarding + Stripe | 3. WhatsApp connector | 4. Payment processing | 5. Mobile app (PWA)

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15. "Ship Side Projects with AI" — Educational Course / Template Pack

Confidence: 7/10 | Difficulty: 3/10 | Seed Fit: 6/10 | Asymmetric Upside: Yes

Problem

Thousands of developers have side project ideas but no time to execute them while working full-time. AI coding tools promise to help, but there's no structured methodology for using them as an async engineering partner.

Evidence: The Devin post documents the methodology in detail: "I treated Devin like a skilled engineer who just joined me — capable, but needs context and direction." Identifies the target audience: "If you're in a similar situation — you know what you want to build, you have the technical judgment to review and direct, but you don't have the hours to write every line yourself." The killer pattern is documented: breaking tasks into small PRs, async review loop, orchestrating from mobile.

Users

Full-time devs with side projects | Indie hackers with limited time | Technical founders shipping while fundraising | Devin/Cursor/Copilot users

Solution

Two components: (A) Course teaching the AI Engineering Partner methodology (spec → research → execute → review → merge loop) and (B) Template Pack with reusable PRD templates, agent prompts, and issue templates.

MVP

Expanded blog post + downloadable template pack to validate demand before building full course.

Distribution

The Devin post as lead magnet | Cross-post to HN, r/SideProject | YouTube walkthrough | Newsletter | Indie hacker podcasts

Pricing

Free guide: Blog post + basic templates. Course ($149 one-time / 3x $59): 6 modules. Templates pack only ($29). Coaching ($499): 3x 1-hour calls.

Competition

AI tool docs (tool-specific, not methodology) | Indie hacker communities (no structure) | YouTube tutorials (feature-specific)

First Experiment

Publish expanded guide with downloadable templates. Track downloads. Survey: "Would you pay $149 for a course?"

Roadmap

Expanded guide + templates | 2. Walkthrough video | 3. Template pack launch ($29) | 4. Film course | 5. Full course + coaching launch

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16. WhatsApp Trial Class Booking Connector

Confidence: 6/10 | Difficulty: 4/10 | Seed Fit: 5/10 | Asymmetric Upside: Moderate

Problem

Small academies receive most trial inquiries via WhatsApp. The booking workflow is manual: message → coach responds → back-and-forth scheduling → manual entry → reminder. Highest-friction conversion path.

Evidence: The Devin post lists: "A WhatsApp trial class booking connector (research phase)" as one of 9 completed feature categories. Need identified working directly with the academy coach.

Users

Martial arts academy owners | Small gym owners | Any fitness studio using WhatsApp as primary channel

Solution

WhatsApp Business API connector that parses incoming messages (LLM), checks available slots, confirms bookings, sends reminders. Human fallback for low-confidence intents. Sold standalone or bundled with GymClass.

MVP

WhatsApp webhook → LLM intent parsing → calendar slot check → booking confirmation reply.

Distribution

Bundled with GymClass | Standalone integration for Mindbody, ZenPlanner | BJJ communities

Pricing

Standalone ($19/mo): Up to 200 conversations. GymClass bundle: Included in Academy tier.

Competition

WhatsApp Business API (raw, needs dev) | ManyChat/Chatfuel (generic chatbots) | Manual process (hours per week)

First Experiment

Interview 5 academy owners: "How do you handle WhatsApp trial inquiries?" Measure time spent. Demo auto-booking in 3 taps. "Would you pay $19/mo?"

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Rankings Addition

| # | Opportunity | Confidence | Difficulty | Seed Fit | Asymmetric Upside |
|---|-------------|------------|------------|----------|-------------------|
| 14 | GymClass Martial Arts Booking SaaS (NEW) | 8/10 | 6/10 | 4/10 | Yes — codebase exists, real users, underserved niche |
| 15 | "Ship Side Projects with AI" Course (NEW) | 7/10 | 3/10 | 6/10 | Yes — author expertise + teaching background |
| 16 | WhatsApp Trial Connector (NEW) | 6/10 | 4/10 | 5/10 | Moderate — works best as GymClass feature |