Slow Shutter mode used to be seamlessly embedded in manual controls, however this made it somewhat more difficult to find if you didn't already have manual controls enabled.

In Camera+ 2 we have added Slow Shutter as an actual shooting mode that can be selected by tapping the "+" to the right of the shutter button. Once you're in Slow Shutter mode, as long as your device supports it, you will be able to set your shutter speed for as long as 30 seconds.