I also have the Bose ear bud. They are called Stay hear ear pieces and i use them everyday at the gym. NEVER have they ever fallen out and sometimes i forget i have anything in my ear. They are that comfortable, And They sound great. Bose has a new set out for sports and sweat but i have been using the Bose Mie2i for almost a year now. I used them with my 4s and now with my 5. Still perfect.
ONE note though. Some people complain that they quit working after time and they think its from sweat... When i had my iphone 4s my bose quit working. I had sound but i could not answer a call, change volume and so on... So i went and bought a new pair and they worked the same. Or i should say did not work the same. So then i figured it was my iphone. I kept the new set of bose and just put them back in the box for a spare. I started to clean my iphone and noticed pocket lint in the head phone jack port. once i cleaned it all out my bose head phones worked perfect again. And now with the iphone 5 i still keep my head phone jack port all cleaned out. Like i said my bose will be a year old next month and they work perfect, and yes they have been exposed to alot of sweat. They truly do take a beating, and will not fall out of your ear.