Camping and travel stores stock a brand called "Design Go". In their range is a hard waterproof case
http://www.design-go.com/detail_38896.html that is ideal for electronic car keys. It cost $10-15 (I don't really remember). They are best worn under a wetty or a tight rashy, otherwise don't hang them around your neck. I've used this for a season without a leak, and I know of other people using them too. Just don't tie it around you neck if you don't have a tight top on, better still, don't tie it around your silly neck at all
(AzzA will not be liable for choked kiddies or idiots out there.)This one is soft and may be able to be cable-tied to a harness
www.design-go.com/detail_38839.html or worn around the hips under boardies.
And please don't play on the road. (It's not that I want your genes to continue swimming in the pool, it's just expensive getting panel work done on metallic paint.)