Do you want to stick a camera outside in a rain storm, but you don't want anything to get wet? Well, you could go out and buy a GoPro camcorder, but those are frightfully expensive (or not, depending on who you are).
The alternate option is to build one yourself. How hard is it? Well, follow the instructions on this page, and you can have your own in under an hour!

Step 1: Drill a hole large enough for your tripod's screw to fit in. This will take a while. Use the knife to make it wider if necessary.

Step 2: Clean off your drill bit if necessary, since plastic bits will lower it's efficiency.

Step 3: Dry-fit your tripod mount. If it doesn't fit, enlarge the hole with the knife. If it is too large, don't worry. Find a nut that will fit the screw.

Step 4: Clean out all the plastic bits using water.

Step 5: Dry-fit the camcorder in using tape. If you want to get fancy you can buy hook and loop fastener.

Step 6: Make sure the back lid closes.

Step 7: Install the mount on the tripod, and make sure it is balanced correctly.

And you are done! Enjoy your waterproof tripod mount!