How to make your iPhone beep every hour?
Well – you can either set up returning alarms – but I suppose you already came up with that idea yourself. Or you can use one of those many many apps for hourly chimes. This overview claims to have a list of over 50 apps doing just that (and more) www.appcrawlr.com/ios-apps/best-apps-hourly-chimes

The first app I see in the list ("chime") seems to be doing exactly what you describe, available on the iTunes App Store at Chime