AudioPen

What they built

AudioPen lets you ramble into your phone and get back clean, reworded text. You talk, it transcribes, and then it rewrites the messy speech into something clear you can actually use. Writers, founders, and students use it to turn a fuzzy thought into a first draft without typing. It is a small, focused AI tool, not a sprawling platform, and Louis Pereira (@louispereira) built and runs it alone.

How they did it

Pereira runs his family's retail business in Goa, India, by day and builds products at night, with no formal engineering background. He set himself a public challenge to go from idea to revenue in a single 12-hour build, streamed the thread live on X, and shipped AudioPen. Because he had spent months building an audience in public first, he had people ready to buy. He reached 100 paying customers within two days of launch, on the back of a following of 10,000-plus that he had earned by sharing his work openly.

The numbers

• AudioPen generates between $15K and $20K a month, run solo, per his Indie Hackers write-up. source
• Built the first version in a 12-hour public hackathon, going from idea to paying customers in days.
• Hit 100 paying customers within 48 hours of launch, thanks to an audience built in public beforehand.

AudioPen is the build-in-public playbook in miniature: earn an audience first, ship a sharp little tool fast, and let the people already watching become your first customers.