Dan Bricklin is sort of a big deal in the technology industry. He came up with the first spreadsheet software for personal computers, Visicalc—which many consider the first killer app. Bricklin has been involved with several different software companies, and he’s been writing about technology on his website for the past ten years. Now he’s setting his sights towards the iPhone.

Bricklin’s first iPhone app, Note Taker (check out the free lite version, $1.99 for the full version) recently hit the App Store, and it’s quickly becoming one of the most popular productivity apps. The software allows you to jot down notes quickly by tracing words directly on your iPhone’s screen. Bricklin was never satisfied with soft or hard keyboards on mobile devices, and he wanted to introduce a simpler alternative for text input.

Speaking to the Boston Globe, Bricklin talked about his ideas for the future of mobile application development:

It’s clear to me that we’re in the post-PC era. The locus of computing power is moving to the pocket. This is how we’re going to do computing, and there will be big businesses built here — $100 million businesses. There will be businesses of the size that you saw in the PC software business, centered around mobile phones.

Check out Bricklin’s blog post announcing and explaining Note Taker, and a video of it in action below.