http://www.amazon.com/Kinivo-BTH240-Bluetooth-Stereo-Headphone/dp/B00AWIPITSI use these Kinivo BTH240's...
never heard of them before purchasing, but read reviews on fitness forums and decided to take a chance since they are only $25
Sound quality is pretty good. Nothing fancy, doesn't hit super low bass but I'm not necessarily looking for that when I'm lifting... I don't do any cardio so I can't review if they stay on well while running.
They keep sweat out of your ears and are very comfortable, although if you have a large head you may want to look elsewhere... I would consider my head size average lol I'm talking that Mike Ditka-sized head
Battery life is awesome... I charge these bad boys once a week and am at the gym 5 days for 2 hours at a time... never died on me. Maybe once they get older the battery will start simmering down, who knows.
IMO, can't go wrong with these for the price. Bluetooth, too!