Invoice Creator for Freelancers

I keep my eyes open for one-person software companies doing creative marketing. Here's an excellent example I stumbled upon this morning.

It's a one-page tool for creating invoices. No sign-in, no subscription, just a simple one page web-app, perfect for freelancers who have to generate an invoice only once a month or so and are currently doing it manually in a word processor. That is, me, until I gave up the freelance work a few months ago to concentrate on Poker Copilot.

The marketing idea is, you get hooked on using the invoice generator, you love it, you tell your friends, you blog about it. And each time you use it, you are shown adverts for the main product, Accounting ASAP.