Riding your bike with ear buds or headphones is actually pretty dangerous. You’re practically signing up for a ride on the front end of a semi coming up behind you.
However, there is now a more chic option – the Cy-Fi Sports Speaker. It’s about the size of a deck of cards and weighs four ounces. It’s waterproof and comes in two versions: a Bluetooth-enabled one and an iPod-specific one.
But it here for $180-$200.
Source: Cy-Fi Speakers