Flexible Block Planner Instead of Time Blocking: startup idea with real demand

Flexible Block Planner Instead of Time Blocking is a startup idea for knowledge workers and people with ADHD. Classic time-blocking doesn't fit people who naturally group tasks into flexible blocks ('work 4 hours, clean, portfolio') rather than planning by the hour. A thread in r/productivity drew 29 upvotes and 32 comments between Sep 14, 2026 – Oct 14, 2026. People get by with Sunsama, Akiflow, and Todoist, and that still leaves this job open. Hotness is 2.40, Cool. Mild annoyance. Price-sensitive audience. The thread drew 29 upvotes and 32 comments. Crowded with decent tools. Buildable in days. A first version is weekend-easy, about 2 weeks, priced under $10 a month and charged as a free tier and a paid upgrade. The pain, the source, the alternatives, the scope notes, and the questions on this page are free to read and free to build from. The agent starter prompt is the paid part. The first slice is on the page. One credit unlocks the rest, to paste into a coding agent, download as Markdown, or send as a private link.

Weekend-easy 2 weeks MVP Web app verified Oct 14, 2026

Verbatim quotes are added only after a manual check. Until then, the thread title is the excerpt. Exact post date and verbatim quotes pending enrichment.

Who has it

Knowledge workers and people with ADHD.

What people use now

Sunsama
Akiflow
Todoist

A way through

A planner built around flexible, reorderable activity blocks without fixed start times: a middle format between a to-do list and a calendar.

MVP scope

Give knowledge workers and people with ADHD a way to do this in one sitting: Plan your day as reorderable blocks of work with no fixed start times, halfway between a to-do list and a calendar.
Persist the result and show it again after a reload.
State the empty case when there is nothing to show yet, with one next step.
Charge later with a free tier and a paid upgrade, under $10 a month. The free path must finish the core job once.
Ship the web app only. Leave Sunsama to keep the jobs they already do well.

How it could charge

Freemium · Under $10 a month · B2C · GLOBAL.

Hotness 2.40

2 of 5, Cool. Mild annoyance. Price-sensitive audience. The thread drew 29 upvotes and 32 comments. Crowded with decent tools. Buildable in days.

Why this score

Pain	2 / 5
Willingness to pay	2 / 5
Demand	1 / 5
Competition gap	2 / 5
Ease of build	5 / 5
Recency	5 / 5

Weights: pain 25%, willingness to pay 20%, demand 20%, gap 15%, ease 10%, recency 10%. Recency is recomputed every build. The source report’s 1–10 score is not shown.

Questions

Is this idea already taken?

People already use Sunsama, Akiflow, Todoist. Those options do not do the job in the solution above. The idea is free to build. Nothing here is an exclusive claim.

How hard is a first version?

Weekend-easy. A tight MVP is about 2 weeks (2 weeks), assuming the regulated or partner-gated parts are stubbed. The paid prompt turns that into tasks.

Who would pay, and how?

The audience is knowledge workers and people with ADHD. Charge a free tier and a paid upgrade, and test a price under $10 a month. Willingness to pay is one input to Hotness, not a promise that someone will buy.

Can I use the evidence?

Yes. Build the product. The thread title is a short excerpt with a link, not a quote we are putting in someone's mouth. Exact post dates and verbatim lines are added only after a manual check. Ideas are suggestions, not medical, legal, or financial advice.

Agent prompt

The first slice is public. The rest is fetched only after you unlock it, and it is not in this page’s HTML.

prd.md

# Agent starter prompt: Flexible Block Planner Instead of Time Blocking

You are a senior product engineer. Build only the product described in this document. If a detail is missing, choose the smallest option and write it down in the README. Do not invent a second product, a marketplace of marketplaces, or a growth hack.

## Product
Name: Flexible Block Planner Instead of Time Blocking
One line: Plan your day as reorderable blocks of work with no fixed start times, halfway between a to-do list and a calendar.
Shape: Web app
AI stance: No AI needed
Region for v1: Global
Hotness (context only, not a requirement): 2.40 (cool). Mild annoyance; price-sensitive audience; thread engagement 29▲/32💬 (demand 1/5); crowded with decent tools; buildable in days.

## Problem
Classic time-blocking doesn't fit people who naturally group tasks into flexible blocks ('work 4 hours, clean, portfolio') rather than planning by the hour.

Who feels it: Knowledge workers and people with ADHD.

Unlock the rest with 1 credit.

The sister site keeps a free plan and a free growth prompt for the same pain. Draft the business plan

Productivity & Notes3.30