Building a shampoo dispenser

Hi,



I'm currently in the process of making my own shampoo dispenser for my shower because when using shampoo there is problems getting all the shampoo out of the bottle. I'm going to make it dispense the shampoo using a sensor. There will be different settings for the length of someones hair, i.e. short, medium, and long. It will be attached to the shower wall using either suction cups or adhesive.



Instead of using a bottle of shampoo I want it to to use sachets. There will be rollers that roll out the shampoo out of the sachet but I think this is flawed. The whole idea is to reduce the amount of shampoo left in the bottle, thus saving money in the long run.



Problems:

I am not to sure about the device as it will be electrical parts. I don't really know how I will be able to section off the electrical circuit board and power it while making it water proof. Any suggestions?



Any other suggestions to design would be helpful as well.



Thanks