MAYY Studio has LocationAlarm: GPS Arrival Alert (iTunes Link) in the iTunes App Store for FREE for a limited time.

The app uses the iPhone’s GPS to let you know when you have arrived near to your destination, and plays an alarm to let you know. It is perfectly compatible with iOS multitasking, so even if you’re in sleep or lock mode, the alarm can be used reliably. The alarm is perfectly compatible with the iPhone’s silent mode, there’s no need to be worried about bothering people around you – your phone will produce a vibrating alarm instead. Set the location freely, using either “Map” by drag-and-dropping a pin, or with the search function by entering in the place name. Naturally, you can set the message that comes up when you arrive to whatever text you like, so you can even use the alarm as a To-Do List!