NightCap from interealtime.com is in my opinion the best slow shutter speed app currently available for the iPhone, which has just been updated with full iPhone 5 support.
So what's new?
- Full iPhone 5 support
- New iPhone 5 optimised interface with much improved controls
- Supports iPhone 5 High ISO mode (boosts ISO from 800 to 3200)
- New Burst mode (available in settings)
- TIFF and HQ JPEG support for higher photo quality (available in settings)
- More responsive: Exposure time is limited to 1/3s for faster handling and less blur (you can disable this in the settings if you prefer the full 1 second exposure time)
- Photo sharing: Share via email, twitter or facebook
- Photo printing
- Easily open photos in your favourite editing app
- Full iOS 6 support
- Many fixes and improvements