I picked up a waterproof case for my iPhone at the boat show yesterday, and it looks like a good alternative to an Aquapac.
It's from
Over Board. The idea is similar to an Aquapac, except they have their own "slide seal" system which is less fiddly.
They are generally cheaper than the competition, and at a show price of £10 I reckon it's a bargain. Hardly worth buying freezer bags at that price!