@Fred931 Your app would likely be denied as you do not own the Halo trademark.
Of course, give it a try, but you have no legal recourse if they take your app down. You lose your time and investments, poof, just like that.
Do some research and you’ll find information about profitability of iPhone apps. Basically, if you can keep it in the spotlight, you can reap money, but you have a huge chance of not being in that light and thus getting trickles if anything.
And the ad supported method just does not work economically. You would have to serve thousands of ads to each user. So go straight for the pay version and scale it down if you want to release a free demo mode sans ads, which is a great business model for the iPhone.