One of the best thing for spider mites is ladybirds. Natural predation. Im not sure if they would cope very well in the hot , humid environment of the shower though...
The spray from the water could be used to blast off the mites also. I use the same technique with a hose and roses!
I hate bugs!
I thought at first that the shower would be perfect for my ivies but it turns out that the heating in the floor actually dries them out really fast and spider mites attack. But now that I shower my ivies really often, they love it :)