I would add a radio or some waterproof iPod holder with speakers. Then I would put some sort of counter weight system so they don't lean to one side.
Also: Working suction cups.
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Just buy the one that is made to look like breasts. I'd link it, but some may consider it nsfw. But, it looks like rubber boobs that you fill with your shampoo and conditioner. Then you fondle them to get the soap out.