Two alarm clocks I like are iRooster and SimpleTimer. iRooster will play anything from iTunes, and SimpleTimer will play / do pretty much whatever you want at a specified time. In fact, SimpleTimer has a pull-down menu that lists sounds to play.
iRooster is shareware, SimpleTimer is free.
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Edit: Sorry, just noticed ... since you want a repeating timer on each hour, I recommend SimpleTimer over iRooster.