PROBLEM SIGNALS – Dozens of Reddit threads asking specifically for a habit tracker that repeats “every X days”, “every other day”, “custom repeat patterns”, “specific weekdays only”, “x times over y days”, etc. Examples (all 2023-2025):

• r/productivity/16iungn – “Is there a habit tracker with custom repeat patterns? X days …” (165 comments; highest-up-voted answer: ‘Doesn’t exist, I’m also looking’).
• r/androidapps/sqtd9x – “App that sends a reminder every X days/weeks or yearly”.
• r/productivity/1iwmpx5 – “Looking for a habit tracker that repeats tasks every other day”.
• r/productivity/18wx5ch – “Habit tracking apps for doing something X days per year”.
• r/androidapps/vtj12m – “App to remind every X days from WHEN LAST DONE (rolling interval)”.
• r/todoist/1kofm66 – “Extension for habit tracking x days per week/month?”. HN search turns up several Show-HN posts of people building side-projects around similar gaps (e.g. “Show HN: Intervals – a habit tracker that reminds you every n days”). Up-votes 100-200 each. → Clear, recurring pain point not fully solved for many users.

KEYWORD VALIDATION (approximate) Using public keyword tools (Ahrefs/Keyword-Every...