John, thanks for the update and merlinpa1969 yeah was aware of Prowl which is good as a temporary solution though I agree with Aniruddh that this needs to be something done by WHMCS.
Back to the main issue of no update since Dec 2011, perhaps if push notifications are too difficult then sorting out bugs like those just mentioned by Corcorlee or adding new features might be an idea? Surely it's going to get worse with iOS7 in Sep?
Regarding push notifications though, has it really taken 1 1/2 years to not manage to develop this? They're not exactly a new feature of iOS and if it's a stumbling block then at least updating everything else would make customers feel cared about.
What I'm asking for and believe many others are too is a concrete update, eg. 'Push notifications are proving tricky, we are updating the iPhone App (and perhaps making an Android one? [apologies if you've done this and I've missed it]) and the next update will be in August 2013 focussing on bug fixes, iPhone 5 screen size and speed improvements'.