Recently I had to get a replacement music player (primarily for walking and cycling), and I settled on a cheap secondhand Sansa Clip+. When I'm on my bicycle I want to have the player out of the way, under my shirt - it's on random anyway, and I never look at it. But I sweat a lot, and the clip+ has some unprotected openings (a mini-usb socket and a micro-sd slot).

My solution: cut a finger from a rubber glove and, well, roll it on :-)

And now for some Totally Unimportant Facts: The French wikipedia page on condoms has substantially more instructional pictures than the german or english ones. the german page at least prominently links to usage instructions on wikibooks.