So by signing this NDA, you are very likely (in effect) saying that you won't release your app or discuss it. It depends on the exact wording, though.
If your app is important to you, you need do one or more of the following:
1. Ask the company directly about the release of your app and get it in writing that your app is not their property and that you can release it without violating agreements with them.
2. Talk to a lawyer
(I'm not a lawyer and am not giving you legal advice)
1. He's based in a totally different country, I'm in Canada and he might as well be based in Japan (an example but close enough).
2. The chances of him discovering the app are slim.
3. The chances of him finding out the I created the app are even slimmer, and because the app isn't a direct competitor the chances of him looking up who founded the company isn't likely.
I think based on those 3 points, my odds are good. But I truly appreciate the dialog here because it got me thinking.