I've worked on battery powered waterproof products and I we had good success with with a two shot moulded enclosure. The inner part was transparent polycarbonate and the outer part was self coloured silicone rubber. There was no rubber over the display, so you get a waterproof window with no joints to seal at no additional cost. By leaving holes in the hard polycarbonate, you can actuate push button switches through the flexible silicone rubber, again at no cost and with no joints to seal. The whole enclosure comprised of two parts, screwed together with am o-ring type seal between the parts. This solution is only cost effective though if your volume supports the tooling costs.

Sticking a knob through the enclosure would be undesirable, but do you need a knob? Our experiments showed that a capacitive touchscreen works through the polycarbonate.

I've also recently seen the performance of wireless power transfer systems, so I was wondering if a dock or stand would be acceptable.