What an interesting question you ask!
Let's start with the most important question, about intellectual property. To be frank, there's always some risk when you hire an outside person to code for you, but I think that the risk is probably relatively minimal. The reality is that ideas are a dime a dozen anyway, and just about anyone who can program an iPhone app is probably busy developing 3-4 ideas of their own anyway!
In fact, from my own experience searching for an Apple iPhone developer who can help me with an AskDaveTaylor-related application, the hard part is finding a good programmer who will be able to achieve your vision for the game/program without asking for premium rates for their quite in-demand skills.
Let's go back to the intellectual property issue for a minute, though. One way you can protect yourself is to establish a reliable method of proving that you invented said game or application on a specific date. The easiest way is to simply write it down and mail it to yourself then leave the envelope unopened. The postmark establishes legal proof of when you inserted the contents and if you were in court, you could then open the envelope and show the judge you had the idea first.
A more formal version of this tactic is to have a very detailed specification that you print and mail to a lawyer friend (to establish the date of invention) prior to hiring a programmer. They just toss it in a file drawer with the same net effect. Again, it could also protect you if they ever claimed it was their idea or they'd already thought of it before you contacted them.
Finally, when you're interviewing potential software developers, if you're really worried that it's a million-dollar idea then play a bit coy when you're interviewing people ("I have an idea for a game kind of like Pac-Man meets Super Mario Cart" rather than "I attach my detailed spec of the game: are you interested?")
Good luck, and let us know how it goes.
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I would like to point out that the Patent and Trademark Office does not recognize the mail your self a letter method of date of origination.
You should talk to an I.P. lawyer in your state to see what they would do.
one thing you may want to look at is Preregistration, here is a link,
http://www.copyright.gov/prereg/help.html
Again, I.P. lawyers are the best source for information on Copyright Law and the only people who can give you real advice.