Following on from last week's Kola Lens and Flash Colour Filters, the Holga Detachable Lens and Filter does a similar job, but specifically for the Iphone 5.
This little gizmo attaches to your Iphone just like a case does to allow you to create 9 different effects with your camera without using an app. Options include a 60mm macro lens, a dual image lens and a range of different coloured filters.
The case costs £25 from The Conran Shop and comes in a range of colours – check it out here. They only stock a version for the Iphone 5, but you can find cases for the Iphone 4 and 4S on Ebay.