I've created a SABnzbd Client app for iOS. I've worked really hard on it, and I hope you find it genuinely useful! This has been built to be a very stable and fast app.
My only suggestion would be: make it a free download (and ideally release the source as well). While you have every right to sell an iOS client and license it the way you want it to be, I always find it a bit alienating when people try to cash in on a (mobile) front-end to other people's free & open source software. While I'd love to have an iOS client for sabnzbd, I'm not even going to try it out, sorry. Just pay some respect where it's due.
All the best for you and your software either way :-)
Sorry it took so long. Now that NZBMatrix is down, not much point in charging for the app so I removed it from the store. Here's the link on Github for the code: