I've seen two condoms being used to waterproof a mobile phone. First one goes over the botto, and tied in a knot at the top. Second goes over the top and died in a knot at the bottom. Obviously you probably won't want to run about with condoms on your gear but it's an option if it really is bad rain lol
And here was me thinking condoms were good for stopping pregnancy, carrying water & putting over a rifle muzzle lol certainly something to think about but as above, I need to incorporate the antenna & headset pin connector