The Las Vegas Sun is reporting that Harrah's will be launching an iPhone app sometime this month.
This sort of thing is inevitable - I expect more of this to come.
What's not really mentioned in the article though - GPS doesn't really work indoors. On the iPhone, it falls back to cell-tower triangulation which is not very accurate (it could tell you that you were on The Strip but not that you were specifically inside Caesars) - that's a problem that I combat with Vegas Mate too. I'd invest in high-quality interior maps if I could use them that way.
Now, the other way an iPhone can locate itself is through registered Wi-Fi access points - if Harrah's is installing and registering Wi-Fi stations, that would improve the ability to locate indoors (for Vegas Mate too - it all works the same way). That would be great for everyone.
The author also refers to the app 'text messaging' users. I assume they mean Push Notifications, which are like text messages but are not really the same thing. It's a pretty high level article so I guess the specific details aren't too terribly important.
I haven't tried the app yet but I certainly will. In the meantime, the far more comprehensive Vegas Mate is on sale this week for the bargain price of $1.99.
Update: Is this 'Caesars Palace' app on the App Store the app they're talking about? If so, it's already out... and quite basic. Looks like basically a brochure in app form. Also, it appears to download each screen of data as you move through the app. That means it won't work offline for iPod Touch users. If this is the app they're talking about, count me underwhelmed.